The fontch macros allow to change font size and family in any place of a plain TeX document. Sizes of 8, 10, 12, 14, 20 and 24 points are available. A sans serif family (\sf) is defined in addition to the families already defined in plain TeX. Optional support for Latin Modern T1 and TS1 fonts is given. There are macros for non-latin1 letters and for most TS1 symbols. Math mode always uses CM fonts. A command for producing doubled-spaced documents is also provided.