Hi! I added antlr3.jar and so the previous exception is no longer coming. But I get another error. Exception in thread "main" java.lang.NoSuchFieldError: recognizer at org.drools.lang.DRLLexer$DFA18.<init>(DRLLexer.java:3914) at org.drools.lang.DRLLexer.<init>(DRLLexer.java:3565) at org.drools.compiler.DrlParser.getParser(DrlParser.java:78) at org.drools.compiler.DrlParser.parse(DrlParser.java:47) at org.drools.compiler.DrlParser.parse(DrlParser.java:85) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:146) at com.eclipsePractice.AviationQuoteAction.readRule(AviationQuoteAction.java:57) at com.eclipsePractice.AviationQuoteAction.doRun(AviationQuoteAction.java:31) com.eclipsePractice.AviationQuoteAction.generateQuote(AviationQuoteAction.java at com.eclipsePractice.AviationQuoteAction.main(AviationQuoteAction.java:74) I have the following jars in my classpath now. janino.jar, drools-jsr94-3.1.0-M1.jar, drools-compiler-3.1.0-M1.jar, drools-core-3.1.0-M1.jar, drools-decisiontables-3.1.0-M1.jar, antlr.jar, antlr-3.0ea9.jar, commons-logging.jar, commons-lang.jar, antlr-2.7.6.jar, stringtemplate-2.3b7.jar Thanks! Shankar