The activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were studied by histochemical methods in the semicircular canal end organs, the utricle and the saccule of young and old mice. AChE was located on the plasma membrane of efferent nerve terminals beneath vestibular hair cells, and along the basement membrane. In the ampulla, stained efferent terminals were more prevalent on the slopes of the crista than in the central region. In all organs examined, there were no discernible differences in AChE activity between young and old mice. BChE activity was observed in the epithelial light cells and supporting cells of the saccule, utricle, and ampulla. Its distribution was similar in both young and old mice in the ampulla, but decreased significantly with age in the utricle. Preliminary data suggest that BChE activity is also weak in old saccular supporting cells. Unlike the utricle, old saccular light cells retained intense BChE activity.