Extracts of two species of Polygala were subjected to a bioscreening study to detect cytotoxic activity by the brine shrimp lethality bioassay. The results obtained for the crude extracts, hexanic and dichlorometane fractions of Polygala sabulosa Aw. Benn. were promising. These results suggest that in those plant extracts, which showed activity for this bioassay, more specific bioassays should be encouraged, in order to confirm these conclusions.