Danshensu (3-(3,4-dihydroxyphenyl) lactic acid), a natural phenolic acid, is isolated from root of Salvia miltiorrhiza, and is widely used as a traditional Chinese medicine for treatment of various cardiovascular diseases. In the present study, toxicity of danshensu was evaluated in male and female dogs after 3-month continuous intravenous infusion. Beagle dogs were treated with danshensu at doses of 17, 50, and 150 mg/kg/day, and observed for 90 days followed by recovery periods. Measurements included clinical observations, body weight, food consumption, temperature, electro-cardiography (EGC), hematology, blood chemistry, urinalysis, gross necropsy, organ weight, and histopathology. No significant adverse effects on these parameters were observed. The only treatment-related finding was a hard knot at injection site observed in the 150 mg/kg group after 2-3 weeks continuous administration, and returned to normal after 3-4 days withdrawal. From these results, it might be concluded that danshensu did not produce any significant cumulative toxicity at the doses administered, as reflected by the various parameters investigated.