This study was conducted to investigate the antitoxic components in the water extract of the roots of Trichosanthes kirilowii (Cucurbitaceae). The results were as follows: Generally, detoxication effects by the water extract of T. kirilowii increased in proportion to the concentrations. Experimental animals were treated with cadmium and T. kirilowii water extract by oral administration. When 40 mg/kg dosage of T. kirilowii extract was administrated it showed the highest antitoxic effects in metallothionein induction. After the water extract treatment, body weights did not increase in proportion to the extract concentrations. These results suggest that T. kirilowii extract increased metallothionein concentration and decreased the toxicity of cadmium in rats. In vitro the antitoxic activity of water extract of T. kirilowii on NIH 3T3 fibroblasts was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) and SRB (sulforhodamine B protein) assays. The light microscopic study was carried out to observe morphological changes of the treated cells. These results were obtained as follows; The concentration of $10^{-2};mg/ml$ of T. kirilowii extract was shown significant antitoxic activity. The number of NIH 3T3 fibroblasts were increased and tend to regenerate. These results suggest that T. kirilowii extract retains a potential antitoxic activity.