The subacute toxicity of sodium saccharin and 2 hydrolytic derivatives, o-sulfamoylbenzoic acid (Compound I) and ammonium o-carboxybenzene sulfonate (Compound II) was evaluated by feeding each of the compounds alone at a dietary level of 20 000 ppm to both beagle dogs and albino rats. Additionally, groups of dogs and rats were fed combinations of the 3 materials at levels up to 20 000 ppm (2000 ppm sodium saccharin, 9000 ppm of both Compound I and II). Dogs were maintained on the test diets for 16 weeks, rats for 13 weeks. No signs of a pharmacotoxic response to the test materials were observed. Parameters determined for treated animals, including growth, food consumption, hematologic profiles, clinical blood chemistry studies, urinalyses, organ weight and ratio data, and both gross and microscopic pathologic evaluation, were not significantly different from control values. From these findings, it is suggested that there is little toxicologic hazard associated with ingestion of the 2 hydrolytic derivatives of sodium saccharin.