LBD-001, a recombinant human interferon $gamma$ produced by genetically engineered yeast as a host system, was intravenously administered to pregnant female rats (Sprague-Dawley) from day 17 of gestation to day 21 of lactation at dose levels.of $0.35 imes 10^6$, $0.69 imes 10^6$, and $1.38 imes 10^6$ I.U./kg/day. In vasopressin-treated group, vasopressin (5 I.U./kg/day) was intravenously injected only for 5 days of perinatal period. (1) No signicant changes by the treatment of LBD-001 were observed in the body weights, food and water consumption, feeding and nurshing behaviors, and the weights of main organs of mother rats. In vasopressin-treated group, no significant changes were observed except the decrease in the food consumption on day 18 of gestation and one case of abnormal offspring with bleeding spots on the skin. (2) No significant changes in the body weights, survival rates, locomotor activity, emotional development. and the motor coordination of offsprings (F1) by the treatment of LBD-001 were observed except the fact that increase of ambulation in the female offsprings of LBD-001 ($0.69 imes 10^6$ or $1.38 imes 10^6$ I.U./kg/day)-treated groups and the increase of rearing in the males of LBD-($1.38 imes 10^6$ I.U./kg/day)-treated group, and the increase of the weight of liver and ovaries in the female offsprings in the LBD-001 ($1.38 imes 10^6$ I.U./kg/day)-treated group were observed. Altogether, the results show that LBD-001 at the dose of $1.38 imes 10^6$ I.U./kg/day or less does not significantly affect the mother rats and their offsprings (F1) except the minor influences when treated during the perinatal and postnatal period.