diff --git a/packages/zoe/src/contractFacet/internal-types.js b/packages/zoe/src/contractFacet/internal-types.js
index 08996cd60a7..88367d9659e 100644
--- a/packages/zoe/src/contractFacet/internal-types.js
+++ b/packages/zoe/src/contractFacet/internal-types.js
@@ -27,6 +27,8 @@
  * @typedef ZCFZygote
  * @property {(bundle: SourceBundle) => void} evaluateContract
  * @property {(instanceAdminFromZoe: ERef<ZoeInstanceAdmin>,
-      instanceRecordFromZoe: InstanceRecord,
-      issuerStorageFromZoe: IssuerRecords) => Promise<ExecuteContractResult>} startContract
+ *     instanceRecordFromZoe: InstanceRecord,
+ *     issuerStorageFromZoe: IssuerRecords,
+ *     privateArgs: Object=,
+ * ) => Promise<ExecuteContractResult>} startContract
  */
diff --git a/packages/zoe/src/contractFacet/types.js b/packages/zoe/src/contractFacet/types.js
index 587bf006f26..55e641a8e51 100644
--- a/packages/zoe/src/contractFacet/types.js
+++ b/packages/zoe/src/contractFacet/types.js
@@ -208,6 +208,7 @@
 /**
  * @callback ContractStartFn
  * @param {ContractFacet} zcf
+ * @param {Object=} privateArgs
  * @returns {ContractStartFnResult}
  */
 
diff --git a/packages/zoe/src/contractFacet/vatRoot.js b/packages/zoe/src/contractFacet/vatRoot.js
index 4d09920432b..12b38327ebb 100644
--- a/packages/zoe/src/contractFacet/vatRoot.js
+++ b/packages/zoe/src/contractFacet/vatRoot.js
@@ -35,6 +35,7 @@ export function buildRootObject(powers, _params, testJigSetter = undefined) {
     zoeInstanceAdmin,
     instanceRecordFromZoe,
     issuerStorageFromZoe,
+    privateArgs = undefined,
   ) => {
     /** @type {ZCFZygote} */
     const zcfZygote = makeZCFZygote(
@@ -48,6 +49,7 @@ export function buildRootObject(powers, _params, testJigSetter = undefined) {
       zoeInstanceAdmin,
       instanceRecordFromZoe,
       issuerStorageFromZoe,
+      privateArgs,
     );
   };
 
diff --git a/packages/zoe/src/contractFacet/zcfZygote.js b/packages/zoe/src/contractFacet/zcfZygote.js
index c6d5e5c7adf..9493ffe8154 100644
--- a/packages/zoe/src/contractFacet/zcfZygote.js
+++ b/packages/zoe/src/contractFacet/zcfZygote.js
@@ -291,6 +291,7 @@ export const makeZCFZygote = (
       instanceAdminFromZoe,
       instanceRecordFromZoe,
       issuerStorageFromZoe,
+      privateArgs = undefined,
     ) => {
       zoeInstanceAdminPromiseKit.resolve(instanceAdminFromZoe);
       instantiateInstanceRecordStorage(instanceRecordFromZoe);
@@ -299,7 +300,7 @@ export const makeZCFZygote = (
       // Next, execute the contract code, passing in zcf
       /** @type {Promise<ExecuteContractResult>} */
       const result = E(contractCode)
-        .start(zcf)
+        .start(zcf, privateArgs)
         .then(
           ({
             creatorFacet = Far('emptyCreatorFacet', {}),
diff --git a/packages/zoe/src/internal-types.js b/packages/zoe/src/internal-types.js
index b464f947676..45eab73c8d5 100644
--- a/packages/zoe/src/internal-types.js
+++ b/packages/zoe/src/internal-types.js
@@ -178,6 +178,7 @@
  * @param {ZoeInstanceAdmin} zoeInstanceAdmin
  * @param {InstanceRecord} instanceRecord
  * @param {IssuerRecords} issuerStorageFromZoe
+ * @param {Object=} privateArgs
  * @returns {Promise<ExecuteContractResult>}
  *
  */
diff --git a/packages/zoe/src/zoeService/startInstance.js b/packages/zoe/src/zoeService/startInstance.js
index f8baa931649..6d8e7505e49 100644
--- a/packages/zoe/src/zoeService/startInstance.js
+++ b/packages/zoe/src/zoeService/startInstance.js
@@ -1,10 +1,10 @@
 // @ts-check
 
-import { assert, details as X } from '@agoric/assert';
+import { assert, details as X, quote as q } from '@agoric/assert';
 import { E } from '@agoric/eventual-send';
 import { makePromiseKit } from '@agoric/promise-kit';
 import { makeWeakStore as makeNonVOWeakStore } from '@agoric/store';
-import { Far } from '@agoric/marshal';
+import { Far, passStyleOf } from '@agoric/marshal';
 
 import { makeZoeSeatAdminKit } from './zoeSeat';
 import { makeHandle } from '../makeHandle';
@@ -26,6 +26,7 @@ export const makeStartInstance = (
     installationP,
     uncleanIssuerKeywordRecord = harden({}),
     customTerms = harden({}),
+    privateArgs = undefined,
   ) => {
     /** @type {WeakStore<SeatHandle, ZoeSeatAdmin>} */
     const seatHandleToZoeSeatAdmin = makeNonVOWeakStore('seatHandle');
@@ -33,6 +34,16 @@ export const makeStartInstance = (
     const { installation, bundle } = await unwrapInstallation(installationP);
     // AWAIT ///
 
+    if (privateArgs !== undefined) {
+      const passStyle = passStyleOf(privateArgs);
+      assert(
+        passStyle === 'copyRecord',
+        X`privateArgs must be a pass-by-copy record, but instead was a ${q(
+          passStyle,
+        )}: ${privateArgs}`,
+      );
+    }
+
     const instance = makeHandle('Instance');
 
     const zoeInstanceStorageManager = await makeZoeInstanceStorageManager(
@@ -190,6 +201,7 @@ export const makeStartInstance = (
       zoeInstanceAdminForZcf,
       zoeInstanceStorageManager.getInstanceRecord(),
       zoeInstanceStorageManager.getIssuerRecords(),
+      privateArgs,
     );
 
     handleOfferObjPromiseKit.resolve(handleOfferObj);
diff --git a/packages/zoe/src/zoeService/types.js b/packages/zoe/src/zoeService/types.js
index 52613cc263c..fe1f9023695 100644
--- a/packages/zoe/src/zoeService/types.js
+++ b/packages/zoe/src/zoeService/types.js
@@ -111,6 +111,9 @@
  * @param {ERef<Installation>} installation
  * @param {IssuerKeywordRecord=} issuerKeywordRecord
  * @param {Object=} terms
+ * @param {Object=} privateArgs - an optional configuration object
+ * that can be used to pass in arguments that should not be in the
+ * public terms
  * @returns {Promise<StartInstanceResult>}
  */
 
diff --git a/packages/zoe/test/privateArgsUsageContract.js b/packages/zoe/test/privateArgsUsageContract.js
new file mode 100644
index 00000000000..86b927454ca
--- /dev/null
+++ b/packages/zoe/test/privateArgsUsageContract.js
@@ -0,0 +1,14 @@
+// @ts-check
+
+import { E } from '@agoric/eventual-send';
+import { Far } from '@agoric/marshal';
+
+/** @type {ContractStartFn} */
+const start = (_zcf, privateArgs) => {
+  const creatorFacet = Far('creatorFacet', {
+    usePrivateArgs: () => E(privateArgs.myArg).doTest(),
+  });
+  return harden({ creatorFacet });
+};
+harden(start);
+export { start };
diff --git a/packages/zoe/test/swingsetTests/privateArgs/bootstrap.js b/packages/zoe/test/swingsetTests/privateArgs/bootstrap.js
new file mode 100644
index 00000000000..fd98743fef4
--- /dev/null
+++ b/packages/zoe/test/swingsetTests/privateArgs/bootstrap.js
@@ -0,0 +1,22 @@
+import { E } from '@agoric/eventual-send';
+import { Far } from '@agoric/marshal';
+
+export function buildRootObject(vatPowers, vatParameters) {
+  const { contractBundles: cb } = vatParameters;
+  return Far('root', {
+    async bootstrap(vats, devices) {
+      const vatAdminSvc = await E(vats.vatAdmin).createVatAdminService(
+        devices.vatAdmin,
+      );
+      const zoe = await E(vats.zoe).buildZoe(vatAdminSvc);
+      const installations = {
+        privateArgsUsageContract: await E(zoe).install(
+          cb.privateArgsUsageContract,
+        ),
+      };
+
+      const aliceP = E(vats.alice).build(zoe, installations);
+      await E(aliceP).privateArgsUsageTest();
+    },
+  });
+}
diff --git a/packages/zoe/test/swingsetTests/privateArgs/test-privateArgs.js b/packages/zoe/test/swingsetTests/privateArgs/test-privateArgs.js
new file mode 100644
index 00000000000..f2bb81bbbf9
--- /dev/null
+++ b/packages/zoe/test/swingsetTests/privateArgs/test-privateArgs.js
@@ -0,0 +1,76 @@
+/* global __dirname */
+
+// TODO Remove babel-standalone preinitialization
+// https://github.com/endojs/endo/issues/768
+import '@agoric/babel-standalone';
+// eslint-disable-next-line import/no-extraneous-dependencies
+import '@agoric/install-ses';
+// eslint-disable-next-line import/no-extraneous-dependencies
+import test from 'ava';
+// eslint-disable-next-line import/no-extraneous-dependencies
+import { buildVatController, buildKernelBundles } from '@agoric/swingset-vat';
+import bundleSource from '@agoric/bundle-source';
+
+const CONTRACT_FILES = ['privateArgsUsageContract'];
+
+test.before(async t => {
+  const start = Date.now();
+  const kernelBundles = await buildKernelBundles();
+  const step2 = Date.now();
+  const contractBundles = {};
+  await Promise.all(
+    CONTRACT_FILES.map(async settings => {
+      let bundleName;
+      let contractPath;
+      if (typeof settings === 'string') {
+        bundleName = settings;
+        contractPath = settings;
+      } else {
+        ({ bundleName, contractPath } = settings);
+      }
+      const source = `${__dirname}/../../${contractPath}`;
+      const bundle = await bundleSource(source);
+      contractBundles[bundleName] = bundle;
+    }),
+  );
+  const step3 = Date.now();
+
+  const vats = {};
+  await Promise.all(
+    ['alice', 'zoe'].map(async name => {
+      const source = `${__dirname}/vat-${name}.js`;
+      const bundle = await bundleSource(source);
+      vats[name] = { bundle };
+    }),
+  );
+  const bootstrapSource = `${__dirname}/bootstrap.js`;
+  vats.bootstrap = {
+    bundle: await bundleSource(bootstrapSource),
+    parameters: { contractBundles }, // argv will be added to this
+  };
+  const config = { bootstrap: 'bootstrap', vats };
+  config.defaultManagerType = 'xs-worker';
+
+  const step4 = Date.now();
+  const ktime = `${(step2 - start) / 1000}s kernel`;
+  const ctime = `${(step3 - step2) / 1000}s contracts`;
+  const vtime = `${(step4 - step3) / 1000}s vats`;
+  const ttime = `${(step4 - start) / 1000}s total`;
+  console.log(`bundling: ${ktime}, ${ctime}, ${vtime}, ${ttime}`);
+
+  t.context.data = { kernelBundles, config };
+});
+
+async function main(t, argv) {
+  const { kernelBundles, config } = t.context.data;
+  const controller = await buildVatController(config, argv, { kernelBundles });
+  await controller.run();
+  return controller.dump();
+}
+
+const expected = ['privateArgs.myArg was accessed in the contract'];
+
+test.serial('private args usage', async t => {
+  const dump = await main(t);
+  t.deepEqual(dump.log, expected);
+});
diff --git a/packages/zoe/test/swingsetTests/privateArgs/vat-alice.js b/packages/zoe/test/swingsetTests/privateArgs/vat-alice.js
new file mode 100644
index 00000000000..0c8edbd1504
--- /dev/null
+++ b/packages/zoe/test/swingsetTests/privateArgs/vat-alice.js
@@ -0,0 +1,29 @@
+import { E } from '@agoric/eventual-send';
+import { Far } from '@agoric/marshal';
+
+const build = async (log, zoe, installations) => {
+  return Far('build', {
+    privateArgsUsageTest: async () => {
+      const privateArgs = harden({
+        myArg: Far('arg', {
+          doTest: () => 'privateArgs.myArg was accessed in the contract',
+        }),
+      });
+      const { creatorFacet } = await E(zoe).startInstance(
+        installations.privateArgsUsageContract,
+        undefined,
+        undefined,
+        privateArgs,
+      );
+
+      const testResult = await E(creatorFacet).usePrivateArgs();
+      log(testResult);
+    },
+  });
+};
+
+export function buildRootObject(vatPowers) {
+  return Far('root', {
+    build: (...args) => build(vatPowers.testLog, ...args),
+  });
+}
diff --git a/packages/zoe/test/swingsetTests/privateArgs/vat-zoe.js b/packages/zoe/test/swingsetTests/privateArgs/vat-zoe.js
new file mode 100644
index 00000000000..be0a4736bbe
--- /dev/null
+++ b/packages/zoe/test/swingsetTests/privateArgs/vat-zoe.js
@@ -0,0 +1,10 @@
+import { Far } from '@agoric/marshal';
+
+// noinspection ES6PreferShortImport
+import { makeZoe } from '../../../src/zoeService/zoe';
+
+export function buildRootObject(_vatPowers) {
+  return Far('root', {
+    buildZoe: vatAdminSvc => makeZoe(vatAdminSvc),
+  });
+}