UNDP/WORLD BANK/WHO Special Programme for Research and Training in Tropical DiseasesCNPq (No. 30.0074/81)FAPESP1. The latex os Euphorbia splendens var. hislopii has a molluscicidal action at low concentration (LD90 less than 1.5 ppm or 1.5 ug/ml) against the vector snails of schistosomiasis. 2. In the present study, the latex in natura or after lyophilization was submitted to the Ames test and the chromotest to evaluate genotoxicity, to the Microtox System to determine acute toxicity, and to the Chinese hamster ovary cell assay (CHO) to measure cytotoxicity. 3. The latex had no mutagenic activity in the presence or abscence of s9 toward the TA98 and TA100 strains os Salmonella typhimurium (Ames test) at concentrations up to 200 ul/plate (in natura) and of 200 ug/plate (lyophilized). The lyophilized latex had no genotoxic activity (Chromotest) and no acute toxic effect on Photobacterium phosphoreum at concentrations up to 445 ug/ml, whereas the sample in natura had a toxic effect with an EC50 of 148,00 ul/l (or ppm). In the CGO/cytotoxicity assay, the lyophilized latex had no cytotoxic effect in quantities up to 200 ug. 4. The latex was found to have no acute toxicity or mutagenic activity at the concentrations os 10 to 12 ug/ml (or ppm) that are being proposed for molluscicidal use in the field.