Purebred female beagles receiving X-irradiation of 100 or 300 r were tested for reproductive ability. The 180 dogs whelped two litters totalling 297 pups. Conception, litter size, pup mortality, and number of weaned pups did not differ significantly between groups. The conclusion is that a female dog surviving total-body X-irradiation at puberty will not suffer loss of fertility to 4 years of age.