Abstract. Grammatica is a prototype implementation of algebraic graph transformation based on relation algebra. It has been implemented using Mathematica on top of the Combinatorica package, and runs therefore on most platforms. It consists of Mathematica routines for representing, manipulating, displaying and transforming graphs, as well as routines implementing some relation algebra-theoretic operations on graphs. It supports both interactive and automatic application of double-pushout graph productions, being therefore both a teaching aid and a research tool for algebraic graph transformation.