Granule cell neurogenesis occurs in the dentate gyrus of the mammalian hippocampus throughout adult life, and incorporation of bromodeoxyuridine (BrdU) into DNA can serve as a marker of cell division associated with such neurogenesis. We examined the effects of a stressor (3h of restraint) on hippocampal cell proliferation in Sprague-Dawley rats and C57BL/6J mice. Animals were killed immediately following restraint stress and their brains were prepared for immunohistochemical studies. Restraint stress caused similar significant increases in c-Fos immunoreactivity among cells in the hypothalamic paraventricular nucleus of both species, indicating that the stress experienced was similar. The restraint procedure also caused a significant decrease in BrdU labeling in the dentate gyrus of rats, as previously reported, but a significant increase in the same region in mice. Hippocampal cell proliferation appears to respond differently to restraint stress in these species.