Hippocampal cell proliferation and concomitant motor activity were examined in adult male mice (C57BL/6J) across a 12:12h light-dark cycle. 5-Bromo-2'-deoxyuridine (BrdU) (200 mg/kg, i.p.) was administered at six equally spaced time points across 24h. A significant change in cell proliferation was found in the hilus (light phase>dark phase), but not in the granule cell layer (GCL)/subgranular zone (SGZ). Since it is generally believed that proliferating cells in the hilus and GCL/SGZ give rise primarily to glia and neurons, respectively, these data suggest a possible circadian influence on gliogenesis, rather than neurogenesis.