Hello, I have a little test case as follows: import org.drools.builder.KnowledgeBuilderConfiguration; import org.drools.builder.KnowledgeBuilderFactory; import org.junit.Assert; import org.junit.Test; public class TestDrools5Config { @Test public void testConfig() { KnowledgeBuilderConfiguration knowledgeBuilderConfiguration = KnowledgeBuilderFactory.newKnowledgeBuilderConfiguration(); knowledgeBuilderConfiguration.setProperty("drools.dialect.java.compiler", "JANINO"); knowledgeBuilderConfiguration.setProperty("drools.dialect.java.lngLevel", "1.6"); String droolsDialectJavaCompiler = knowledgeBuilderConfiguration.getProperty("drools.dialect.java.compiler"); System.out.println("droolsDialectJavaCompiler=" + droolsDialectJavaCompiler); Assert.assertNotNull(droolsDialectJavaCompiler); String droolsDialectJavaLngLevel = knowledgeBuilderConfiguration.getProperty("drools.dialect.java.lngLevel"); System.out.println("drools.dialect.java.lngLevel=" + droolsDialectJavaLngLevel); Assert.assertNotNull(droolsDialectJavaLngLevel); } } It fails. I have seen the post for using JANINO with Drools: http://lists.jboss.org/pipermail/rules-users/2009-February/008089.html Yet this does not explain my test case failing - any ideas. It appears as if it is not possible to set JANINO programmatically, only via properties.conf, etc. which I don't want to do(!) Cheerio, Nic Hemley