It would be great if you could add one of the following two paragraphs to the PLT Scheme Reference section <a href="http://1.1.13.">1.1.13.</a> 1.  PLT Scheme supports true native / OS threads meaning that multiple core CPU's are fully taken advantage of. -or- 2.  PLT Scheme simulates threads within scheme in an OS portable way.  All scheme threads run within one (or a small or limited number) of OS threads.  Multi-core CPU's are therefore not fully utilized. Many Scheme's and Lisp's out there say they support threads but how they do this (cooperative/pre-emptive, native/simulated) makes all the difference in the world.  Sadly, virtually no one's documentation makes it clear what you are dealing with.  Adding the above text would clarify the matter. Thanks. Blake McBride