History and Acknowledgements: Poly/ML was originally written by David Matthews at the Computer Laboratory at Cambridge University. It was written in an experimental language, Poly, similar to ML but with a different type system. Among the first users was Larry Paulson who used it to develop the Isabelle theorem prover. It was licensed by Cambridge University’s company Cambridge University Technical Services, then called Lynxvale, to Abstract Hardware Limited (AHL) who developed it further and used it to write the Lamba system for hardware verification as well as other tools. Mike Crawley did significant work on the run-time system and Simon Finn was heavily involved in translating Poly/ML from Poly into Standard ML. Nick Chapman (nic AT truthmachine DOT demon DOT co DOT uk) wrote the C-language interface. In 1999 AHL’s rights in Poly/ML were acquired by CUTS and they agreed to make Poly/ML freely available. More recently David Matthews has continued to develop Poly/ML. The Standard Basis Library has been implemented and the compiler converted to the 1997 Definition of Standard ML (Revised). This work was supported in part by LFCS. The most recent work has been rewriting the run-time system which has resulted in the version 5 release. This work was supported by the Verisoft project and the Technical University of Munich.