Danshensu (3-(3,4-dihydroxyphenyl) lactic acid), a natural phenolic acid, is isolated from Salvia miltiorrhiza root, and is the most widely used traditional Chinese medicine for the treatment of various cardiovascular diseases. It has been reported to have potential protective effects from oxidative injury. However, there is a little information about its possible toxicity. In this study, acute and subchronic toxicity of danshensu in mice and rats have been evaluated. In the acute study, danshensu intraveniouslly administered to rats failed to induce any signs of toxicity or mortality up to a maximum practical dosage of 1500 mg/kg body weight. Test substance administered acutely to mice caused dose-dependent general behavior adverse effects and mortality with the medial lethal dose of 2356.33 mg/kg. The no observed adverse effect level and the lowest observed adverse effect level were 1835 mg/kg and 2000 mg/kg, respectively. In the subchronic study, rats were tested by daily intraperitoneal injection of danshensu at the doses of 50, 150, and 450 mg/kg for 90 days, resulting in no mortality, no changes in body weight, food consumption, hematological and serum chemistry parameters, organ weights, or gross pathology or histopathology. The only treatment-related finding was transient writhing response observed in the 450 mg/kg group after administration.