Six mutagenic and/or carcinogenic agents were tested for their ability to cause somatic eye mutation (red sectors on a yellow eye) in Drosophila melanogaster. Results were analysed by the Chi-squared method and by the Kolmogorov - Smirnov two-sample (non-parametric) test. Methyl methanesulphonate, cyclophosphamide, acriflavine and procarbazine were active, whereas acetamide and tetracycline failed to elicit a significant response. Thus, relative to other mutagenicity assays, this somatic system seemed to possess no special ability to correctly identify carcinogens because both acriflavine and acetamide were misidentified on a carcinogenicity basis. However, it could be a suitable alternative to the recessive lethal test for mutation, because of its technical simplicity and rapidity, subject to an increase in the size of the data base.