diff --git a/benchmarks/src/main/java/io/prometheus/client/benchmark/SanitizeMetricNameBenchmark.java b/benchmarks/src/main/java/io/prometheus/client/benchmark/SanitizeMetricNameBenchmark.java
new file mode 100644
index 000000000..d89e676e5
--- /dev/null
+++ b/benchmarks/src/main/java/io/prometheus/client/benchmark/SanitizeMetricNameBenchmark.java
@@ -0,0 +1,53 @@
+package io.prometheus.client.benchmark;
+
+import com.codahale.metrics.MetricRegistry;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+import org.openjdk.jmh.runner.options.TimeValue;
+
+import io.prometheus.client.Collector;
+
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Benchmark)
+public class SanitizeMetricNameBenchmark {
+
+  @Benchmark
+  @BenchmarkMode({ Mode.AverageTime })
+  @OutputTimeUnit(TimeUnit.NANOSECONDS)
+  public void sanitizeSanitizedName() {
+    Collector.sanitizeMetricName("good_name");
+  }
+
+  @Benchmark
+  @BenchmarkMode({ Mode.AverageTime })
+  @OutputTimeUnit(TimeUnit.NANOSECONDS)
+  public void sanitizeNonSanitizedName() {
+    Collector.sanitizeMetricName("9not_good_name!");
+  }
+
+  public static void main(String[] args) throws RunnerException {
+
+    Options opt = new OptionsBuilder()
+        .include(SanitizeMetricNameBenchmark.class.getSimpleName())
+        .warmupIterations(5)
+        .measurementIterations(4)
+        .measurementTime(TimeValue.seconds(1))
+        .warmupTime(TimeValue.seconds(1))
+        .threads(4)
+        .forks(1)
+        .build();
+
+    new Runner(opt).run();
+  }
+}
diff --git a/simpleclient/src/main/java/io/prometheus/client/Collector.java b/simpleclient/src/main/java/io/prometheus/client/Collector.java
index 3a69500dc..6f84e1840 100644
--- a/simpleclient/src/main/java/io/prometheus/client/Collector.java
+++ b/simpleclient/src/main/java/io/prometheus/client/Collector.java
@@ -352,16 +352,24 @@ protected static void checkMetricName(String name) {
     }
   }
 
-  private static final Pattern SANITIZE_PREFIX_PATTERN = Pattern.compile("^[^a-zA-Z_:]");
-  private static final Pattern SANITIZE_BODY_PATTERN = Pattern.compile("[^a-zA-Z0-9_:]");
-
   /**
    * Sanitize metric name
    */
   public static String sanitizeMetricName(String metricName) {
-    return SANITIZE_BODY_PATTERN.matcher(
-            SANITIZE_PREFIX_PATTERN.matcher(metricName).replaceFirst("_")
-    ).replaceAll("_");
+    int length = metricName.length();
+    char[] sanitized = new char[length];
+    for(int i = 0; i < length; i++) {
+      char ch = metricName.charAt(i);
+      if(ch == ':' ||
+          (ch >= 'a' && ch <= 'z') ||
+          (ch >= 'A' && ch <= 'Z') ||
+          (i > 0 && ch >= '0' && ch <= '9')) {
+        sanitized[i] = ch;
+      } else {
+        sanitized[i] = '_';
+      }
+    }
+    return new String(sanitized);
   }
 
   /**
diff --git a/simpleclient/src/test/java/io/prometheus/client/CollectorTest.java b/simpleclient/src/test/java/io/prometheus/client/CollectorTest.java
index dbf611322..73603a37c 100644
--- a/simpleclient/src/test/java/io/prometheus/client/CollectorTest.java
+++ b/simpleclient/src/test/java/io/prometheus/client/CollectorTest.java
@@ -9,6 +9,32 @@
 import static org.junit.Assert.*;
 
 public class CollectorTest {
+
+  @Test
+  public void sanitizeMetricPrefix() throws Exception {
+      assertEquals("afoo", Collector.sanitizeMetricName("afoo"));
+      assertEquals("zfoo", Collector.sanitizeMetricName("zfoo"));
+      assertEquals("Afoo", Collector.sanitizeMetricName("Afoo"));
+      assertEquals("Zfoo", Collector.sanitizeMetricName("Zfoo"));
+      assertEquals(":foo", Collector.sanitizeMetricName(":foo"));
+
+      assertEquals("_foo", Collector.sanitizeMetricName("0foo"));
+      assertEquals("_foo", Collector.sanitizeMetricName("5foo"));
+      assertEquals("_foo", Collector.sanitizeMetricName("9foo"));
+      assertEquals("_foo", Collector.sanitizeMetricName("/foo"));
+      assertEquals("_foo", Collector.sanitizeMetricName("*foo"));
+  }
+
+  @Test
+  public void sanitizeMetricBody() throws Exception {
+      assertEquals("aamzAMZ059", Collector.sanitizeMetricName("aamzAMZ059"));
+      assertEquals("aaMzAmZ009", Collector.sanitizeMetricName("aaMzAmZ009"));
+      assertEquals("aZmA950aMz", Collector.sanitizeMetricName("aZmA950aMz"));
+      assertEquals("aZ9mA0a5Mz", Collector.sanitizeMetricName("aZ9mA0a5Mz"));
+      assertEquals("aZ9mA_0a5Mz", Collector.sanitizeMetricName("aZ9mA*0a5Mz"));
+      assertEquals("aZ9mA_0a5Mz", Collector.sanitizeMetricName("aZ9mA&0a5Mz"));
+  }
+
   @Test
   public void sanitizeMetricName() throws Exception {
       assertEquals("_hoge", Collector.sanitizeMetricName("0hoge"));