Objectives : The present study has been undertaken to investigate the effects of Leonuri Sibirici Herba and Pruni Persicae Semen on pregnant rats. Method : In this experiment, the pregnant rats were administered by water extracts of Leonuri Sibirici Herba and Pruni Persicae Semen. The levels of weights, ALT, AST, ALP, BUN, creatinine, progesterone, Na and K in serum and reproductive indices of the rats were measured after treatment. Results : 1. The levels of body weight gains were not significantly changed in comparison with Control group in Leonuri Sibirici Herba group and Pruni Persicae Semen group. 2. In the levels of reproductive indices of the rats, the number of corpora lutea, implantation, viable fetuses, pre-implantation loss, post-implantation loss, fetal weight and placental wight were not significantly changed in comparison with Control group in Leonuri Sibirici Herba group and Pruni Persicae Semen group. 3. The levels of BUN, creatine, ALT, AST and ALP were not significantly changed in comparison with Control group in Leonuri Sibirici Herba group and Pruni Persicae Semen group. 4. The level of progesterone was not significantly changed in comparison with Control group in Leonuri Sibirici Herba group and Pruni Persicae Semen group. 5. The levels of Na and K were not significantly changed in comparison with Control group in Leonuri Sibirici Herba group and Pruni Persicae Semen group. Conclusion : Reviewing these experimetal results, it appeared that Leonuri Sibirici Herba and Pruni Persicae Semen had not toxicity on pregnant rats.