A fertility study was carried out in Crj: CD (SD) rats orally administered ranitidine hydrochloride, a histamine H2-receptor antagonist, at dose levels of 50, 200 and 800 mg/kg/day in base weight. Male rats were treated from 60 days before mating until the completion of mating. Female rats were administered ranitidine hydrochloride from 14 days prior to mating up to day 7 of gestation. All pregnant females were sacrificed on day 20 of gestation and all fetuses were examined for abnormalities. Temporary salivation was noted in rats of both sexes given 800 mg/kg/day of ranitidine and in the male rat group given 200 mg/kg/day. No abnormal signs were seen in mating or fertility in the rats treated with ranitidine. No external, internal and skeletal anomalies attributable to ranitidine hydrochloride were observed in the fetuses. It was concluded that ranitidine hydrochloride has no harmful effect on mating, fertilization, implantation, or embryonic development.