This study was conducted to investigate the antitoxic agent in methanol extract of Houttuynia cordata $T_{HUNB}$. Detoxication effects By H. cordata $T_{HUNB}$ extract increased in proportion to the extract concentrations. When 40 mg/kg dosage of H. cordata $T_{HUNB}$ extract was administered, it showed the highest antitoxic effects in metallothionein induction. After the extract treatment, body weights generally increased in proportion to the extract concentrations. From the above results, H. cordata $T_{HUNB}$ extract increased metallothionein concentrations and decreased the toxicity of cadmium in rats. In vitro the antitoxic activity of methanol extract of H. cordata $T_{HUNB}$ on NIH 3T3 fibroblasts was evaluated by the MTT {3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl-2H-tetrazoliumbromide} and SRB (sulforhodamine B protein) assays. The light microscopic study was carried out to observe morphological changes of the treated cells, $10^{-2};mg/ml$ Concentrations of H. cordata $T_{HUNB}$ extract was shown significant antitoxic activity. The number of NIH 3T3 fibroblasts were increased and tend to regenerate. These results suggest that H. cordata $T_{HUNB}$ extract retains a potential antitoxic activity.