In mammals, the loss of vestibular hair cells appears to lead to limited proliferation of supporting cells in vivo.However, recent studies have indicated that active cell proliferation can be induced by brief exposure to forskolin in cultured utricles using the seat culture technique. The aim of this study was to examine whether such cell proliferation in vestibular epithelia could be induced using the standard organ culture. Utricles harvested from Wistar rats at 3 days of age were provided for organ culture. After brief incubation in a medium containing forskolin, utricles were maintained in medium containing fetal bovine serum and bromodeoxyuridine (BrdU) for 72 hrs. Immunohistochemistry for BrdU demonstrated the localization of BrdU-positive cells in cultured utricles, but their number was apparently smaller than that in the study with seat culture reported previously. In addition, only 10% of comprehensive BrdU-positive cells were located within the sensory epithelium. Therefore, the cell proliferation activity in the vestibular epithelium using organ culture differed from that using seat culture, although mammalian vestibular epithelia have the potential for cell proliferation. Elucidating what causes the difference in cell proliferation between organ culture and seat culture will lead to establishment of a strategy for induction of activity cell proliferation in mammalian vestibular hair cells in vivo.