I uploaded test log for IronRuby on Mono, specifically output of "rake test_compiler mono=1". http://sparcs.kaist.ac.kr/~tinuviel/download/IronRuby/test_compiler.log Following scenarios fail; others pass: Scenario_RubyReturnValues2 Scenario_RubyReturnValues3 Scenario_RubyReturnValues4 -- Seo Sanghyeon