Effects of temperature on genotoxic potency of cisplatin were studied in the Drosophila wing spot assay. A fixed concentration of 0.05 mM cisplatin was evaluated for genotoxicity at 4 temperatures (18, 20, 25, and 29 degrees C). The compound was found to be a positive inducer of all three endpoints at all temperatures when compared to the water controls. While no effect of temperature was found on the percentages of cisplatin-treated wings with small spots, there were significant effects for large spots and twin spots. The capacity of cisplatin to induce both large spots and twin spots tended to increase with rising temperature. A significant linear regression was obtained in regard to temperature and number of cisplatin-induced large spots per wing. The lack of any effect of temperature on induced small spots provides additional evidence that small spots may be qualitatively different from large spots and twin spots. The observed enhancement by higher temperature of cisplatin's genotoxic potency is likely due in part to increased cellular uptake of the mutagen. Wide temperature fluctuations should be avoided when conducting the wing assay. Although the customary temperature for performing the assay has been within the range 24-25 degrees C, the optimum temperature for maximizing genotoxic potency (and sensitivity of the assay) may be nearer 27 degrees C.