The administration of adult physiological levels of testosterone (T) and 17ß-estradiol (E₂) to male Siberian hamsters was previously shown to delay the onset of puberty. To examine if this is a response common to other rodents, we investigated if exogenous steroids also alter the onset of puberty in Syrian hamsters and mice. Juvenile male Syrian hamsters and mice were implanted with silastic capsules containing T, E₂, or cholesterol control. After 15 days, plasma, pituitaries, and testes were processed for histological analysis or measurements of gonadotropins and circulating steroid hormones. T and E₂ implants reduced testes mass and gonadotropin stores in both species and arrested spermatogenesis in Syrian hamsters. By contrast, spermatogenesis in mice was unaffected by T and only modestly affected by E₂. Although E₂ inhibited circulating follicle-stimulating hormone (FSH) in both species, T inhibited circulating FSH in mice only. Overall, our results demonstrate that the hypothalamic-pituitary-gonadal axis of each rodent species responds uniquely to T and E₂ during the pubertal transition. Despite the highly varied effects of T and E₂ in these two species, the ability of steroid hormones to disrupt the onset of puberty appears to be a feature common to many rodents.