The Computer-Automated Structure Evaluation (CASE) program has been applied to the analysis of the genotoxic activity of 54 pesticides (31 insecticides, 15 herbicides and 8 fungicides), in 5 different short-term test systems measuring point-gene mutation and DNA damage. The database contains compounds presenting quite diverse structures including carbamates, thiocarbamates, organophosphurus, halo-aromatics and some other functionalities. Some significant relationships between common structural features and the genotoxic activity displayed by these chemicals have been found. Among the most relevant fragments, automatically selected by the program, a methoxyphosphinyl and a chloro-vinyl group appear as the common structural subunits responsible for the activities detected in the battery composed of the Salmonella typhimurium mutagenicity, the Mouse Lymphoma gene mutation assay and recombinogenicity in the yeast Saccharomyces cerevisiae.