Dimethyl sulfoxide, a solvent commonly used in toxicological studies, was investigated for its cytotoxic potential and its effect on development and reproductive performance in transgenic Drosophila melanogaster (hsp70-lacZ) Bg 9. Various concentrations (0.0, 0.1, 0.3, 0.5, 1.0, 2.0, and 3.0%) of the solvent were mixed with food and fed to the flies and larvae. The toxic effects were studied by examining hatchability, emergence, fecundity, reproductive performance, and hsp70 expression by means of in situ beta-galactosidase staining in the tissues of third-instar larvae and in the reproductive organs of male and female flies of the strain. Our results showed that dimethyl sulfoxide at and above 0.5% of dietary concentration evoked cytotoxicity, as evidenced by hsp70 expression in the larval tissues, and also impaired the development and reproductive performance of the flies. This study suggests that the no observed adverse effect level of dimethyl sulfoxide is 0.3% of dietary concentration for developmental toxicity, reproductive toxicity, and cytotoxicity studies in Drosophila melanogaster.