41 compounds or mixtures of diverse structure and application have been tested for genotoxic activity. The materials were tested in bacterial mutation assays, in Saccharomyces cerevisiae JD1 for mitotic gene conversion and in a cultured rat-liver cell line for structural chromosome damage. 11 compounds were bacterial mutagens, 4 induced mitotic gene conversion in yeast and 5 were positive in the chromosome assay. 5 of the materials were positive in bacteria only and 2 compounds induced chromosome damage in cultured cells in the absence of mutation in bacteria or gene conversion in yeast. The materials were tested over a 5-year period and the performance and evolution of the 3 assays during this time is evaluated. The results are considered in relation to the structure of the chemicals and the genotoxicity of related compounds.