To further characterized the Drosophila bioassay as a screen to detect developmental toxicants, sodium arsenate heptahyrdrate (SAH; CAS 7631-89-2), a documented animal teratogen and developmental toxicant, was evaluated. SAH concentrations ranging from 263-1528 ug/vial were investigated in a series of three experiments using our published protocol (Teratogenesis, Carcinogenesis, and Mutagenesis 11:147-173, 1991). Each experiment utilized five SAH concentrations plus a concurrent control. In the second and thrid experiments, 2-3 concentrations from the preceding experiment were replicated, and 2-3 new higher concentrations were added. Drosophila were exposed throughout development (egg through third instar larva) in culture vials to medium containing SAH. 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 and allowed to oviposit for 20 hours, 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 each experiment, the incidence of the two defects at each concentration was compared to the concurrent control using chi-square. In cases where replicate data were available at a given concentration, incidence data were pooled and compared to the pooled controls. Using pooled data, the incidence of bent bristles was statistically increased at the following SAH concentrations - 389 (21/489, p<0.001) 575 (24/644, p<0.001), 699 (24/520, p<0.001) and 850 (15/479, p<0.001) ug/vial. For non-replicated concentrations, the incidence of bristle defects was significantly increased at 1033 (8/241, p<0.01) and 1528 (11/224, p<0.001) ug/vial. No wing blade defects were observed at any SAH concentration. These results provide additional support for increased utilization of this test as a prescreen for developmental toxicants.