To further characterize the Drosophila bioassay as a screen to detect developmental toxicants, vinblastine sulfate (VBS; CAS No. 143-67-9), a documented teratogen and developmental toxicant, was evaluated. VBS concentrations were investigated in two experiments using our published protocol (Teratogenesis, Carcinogenesis, and Mutagenesis 11:147-173, 1991). Each experiment utilized seven VBS concentrations plus a concurrent control. Initially, concentrations ranging from 40-200 ug/vial were evaluated. Since no flies were found to emerge at concentrations greater than 40 ug/vial, lower concentrations (3-30 ug/vial) were utilized in the second experiment to better characterize any developmental toxicity and to determine if a threshold could be observed. Drosophila were exposed throughout development (egg through third instar larva) in culture vials to medium containing VBS. Each vial contained 1g of powdered medium and 5ml of distilled deionized water or a solution of test chemical in water. A mated, untreated, Oregon-R wild-type female (Mid-American Drosophila Stock Center, Bowling Green State University, Ohio) was added to each culture vial, allowed to oviposit for 20 hours, and then removed. Emerging offspring were collected over 10 days and examined microscopically (25x) for bent humeral bristles and wing blade notches; morphological defects shown to occur with an increased incidence in flies exposed to developmental toxicants. In addition, offspring were also examined for the presence of eye abnormalities after an unusual eye defect was observed in a fly exposed to VBS in the 40 ug/vial group in the first experiment. In each experiment, the incidence of specific defects at each concentration was compared to the concurrent controls using chisquare. The incidence of bristle defects was significantly increased at 10 ug/vial, 15/128, p<0.05 and at 40 ug/vial, 1/5, p<0.001. The incidence of eye defects was significantly increased at 15 ug/vial, 2/78, p<0.05, 20 ug/vial, 2/48, p<0.01, 25 ug/vial, 5/44, p<0.001, and at 40 ug/vial, 1/5, p<0.001. No wing blade defects were observed at any VBS concentration. The results with VBS parallel the developmental toxicity reported in mammals, and replicate and expand published Drosophila data. These findings provide additional support for increased utilization of this assay as a prescreen for the detection of developmental toxicants.