A new composite antibiotic, SM-101(sulbactam.metampicillin), was at dose levels of 0, 250, 500 and 1000 mg/kg/day administered intravenously to Sprague-Dawley male rats from predating to mating period and to females from premating to early gestation period. Effects of test agent on general findings and reproductive performance of parent animals and embryonic development were examined. In male parents, two deaths occurred at 1000 mg/kg. The increase in kidney weight of the 1000 mg/kg group were also observed. The decrease in body weight and food consumption were found at 500 and 1000 mg/kg. The decrease in spleen weight were seen at 250, 500 and 1000 mg/kg. In female parents, three deaths were found at 1000 mg/kg. Mating performance and fertility of parent animals were not adversely affected by all doses tested. F1 fetuses showed no changes related to treatment of SM-101. The results show that the no effect dose level(NOEL) for general toxicity of parent animals is under 250 mg/kg/day and NOELS for reproductive capability and fatal development are over 1000 mg/kg/day.