The effect of water extract of Gynostemma pentaphyllum was evaluated on 6-month chronic toxicity in Wistar rats. Control group received orally 10 ml kg(-1) day(-1). The extract was orally given to the five treatment groups at the doses of 6, 30, 150, 750 and 750 mg kg(-1) day(-1) for 24 weeks. The last group served as the recovery group. The results showed that the extract did not produce any significant dose-related changes. Therefore, it is concluded that the extract of G. pentaphyllum at the given doses did not produce any significant toxic effect in rats during 6-month period of the treatment.