From the homepage:

Gambit is a high-performance implementation of Scheme based on an optimizing compiler. It conforms to the IEEE-Scheme? standard (IEEE P1178) and the Revised^4 Report on Scheme (R4RS). It is almost R5RS compliant and is lacking syntax-rules. The full numeric tower is implemented, including: arbitrary precision integers (bignums), rationals, inexact reals (floating point numbers), and complex numbers. Several extensions to the standards are provided.

(this relates to version 3.0)

Gambit 4

Gambit 3.0 was released in 1998, and Gambit 4 has been in development since then.

Gambit 4.0 was released on August 25th 2007. See

Gambit's website is now wiki-based, and Gambit's source is managed by Mercurial.