Diabetic patients occasionally complains of dizziness and vertigo, which suggests derrangement of vestibular function of inner ear. To examine whether diabetic condition has any relation with the a fine morphology of utricular macula which is the important mechanoreceptor of equilibrium, light and electron microscopic observations were made on neuroepithelium, type I and II hair cells of utricular macula as well as on vestibular nerve in alloxan induced diabetic rats. Abnormal features found were as follows: 1) Myelin lamella of utricular nerve shows frequent interruption, irregular running and ballooning. 2) Otolithic membrane is fractured and fragmented. 3) Chalice of type I hair cell of utricle is swollen. It is suggested that fine morphological changes in the utricular components of alloxan diabetic rat are closely related with the macular function.