UPDATE: This post by the fellow leading the Clojure Alioth effort shows that the JVM GC settings are probably off for some of the benchmarks, http://groups.goog

UPDATE: This post by the fellow leading the Clojure Alioth effort shows that the JVM GC settings are probably off for some of the benchmarks, http://groups.google.com/group/clojure/msg/8de18e3719aa376a http://groups.google.com/group/clojure/msg/8de18e3719aa376a. This shows just how early days it is for Clojure microbenchmarks :) Those are benchmarks for Clojure 1.2.0. The Clojure 1.3.0 alphas introduce quite a few things that specifically make numerical code quite a bit faster as well as boosting overall performance. Being competitive with Scala and Java is a real goal for Clojure so expect the performance story to continue improve for some time. While I don't know of any real-world Clojure cases for mission critical applications - Clojure has been run Azul boxes where the GC is collecting some like 6gbs a sec. Turns out that only takes up about 6% of CPU time. So I think Rich is onto something here about the memory cost of immutable data structures in high performance code and the incredible guarantees of the JVM's GC. On Alioth microbenchmarks you probably won't see those benefits.