When I define a closure and store it to a variable, according to groovy's documentation I can use two ways of calling that closure: closure.call(args) or closure(args). There is a great performance difference between these calls though. The difference consists of: 2 calls to new MissingPropertyException 2 calls to new MissingMethodException 2 calls to InvokeHelper.format(Object arguments, boolean verbose) 12 calls to arg.replaceAll (InvokeHelper:line 600) One problem is the arg.replaceAll in InvokeHelper.format. Formatting the exceptions that are catched inside groovy is totally useless and causes extremely big performance loss. Removing calls to InvokerHelper improves performance a lot. Below an example of the two cases and how they work in different versions of groovy: test.groovy: ------------------------------------ closure = { number -> test = number + 1; } start = java.lang.System.currentTimeMillis() for (i in 0..100000) { closure(1) } end = java.lang.System.currentTimeMillis() test1 = end - start start = java.lang.System.currentTimeMillis() for (i in 0..100000) { closure.call(1) } end = java.lang.System.currentTimeMillis() test2 = end - start println "test1: $test1" println "test2: $test2" -------------------------------------- tested with: blackdown-j2sdk1.4.2_03 and sun's jdk1.5.0_09 groovy-1.0-jsr-04/bin/groovy test.groovy test1: 573 test2: 541 groovy-1.0-jsr-06/bin/groovy test.groovy test1: 30370 test2: 654 groovy-1.0/bin/groovy test.groovy test1: 8455 test2: 615 groovy-1.0-modified/bin/groovy test.groovy test1: 7653 test2: 620 groovy-1.0-modified is the same as 1.0, but MissingMethodException's call to InvokerHelper's methods were removed.