- April 1990, the Haskell Report is released.
- June 1990, Implementations. John Peterson mentions that groups at Yale and Glasgow are working hard on implementing Haskell.
- June 1990, Parallel Haskell. Simon Peyton Jones mentions that a parallel Haskell implementation is already running.
- June 1990, A 3rd Haskell Implementation. Diomidis Spinellis announces that a 3rd Haskell implementation is underway at Imperial College. Notably it compiles to native assembly.
- August 1990, HBC 0.99 (Haskell B Compiler). Lennart Augustsson announces that Lazy ML version 0.99 comes with a free Haskell compiler, hbc.
- Monads popularised by Wadler