A fertility study was carried out in Sprague Daxley rats which have been given the intravenous or intraperitoneal injections of rHuIFN-${alpha}$A, a commecially available therapeutic agent, at dose levels of $1{ imes}10^5$, $4{ imes}10^5$ and $1.2{ imes}10^6$ I.U/kg/day. Male rats were treated with rHuIFN-${alpha}$A from 60 days before pairing and until the completion of mating. Femal rats received rHuIFN-${alpha}$A for 22days prior to mating and up to day of gestation. All pregnant females were sacrificed on day 20 of gestation and all fetuses were examined for abnormalities. Both the male and female animals treated with rHuIFN-${alpha}$A did not show any abnormal responses. No abnormal signs were seen in reproducibility for the rats treated with rHuIFN-${alpha}$A. No External, internal and skeletal anomalies attributable to rHuIFN-${alpha}$A were observed in the fetuses. It was concluded that rHuIFN-${alpha}A$ had no harmful effect on mating, fertilization, implantation, or embryonic development.