AMSTeX is a TeX macro package, originally written by Michael Spivak for the American Mathematical Society (AMS) during 1983- 1985 and is described in the book 'The Joy of TeX'. It is based on Plain TeX, and provides many features for producing more professional-looking maths formulas with less burden on authors. More recently, the focus of attention has switched to amslatex, but AMSTeX remains as a working system.