There are few population based prevalence estimates of stereopsis and most of the studies are in children. A prevalent study in the middle and elderly population was undertaken to highlight the impact of ageing on stereopsis. Six hundred and four persons between 40 and 85 years with 6 / 6 N6 vision and no other pathology, were subjected to Frisby stereotest. Twenty nine percent had full stereopsis (3 plates seen), while 3% had no stereopsis (no plates seen). The prevalence of defective stereopsis increased with age. The incidence of full stereopsis remains the same until the sixties,, followed by an abrupt decrease by half in the seventies (p = 0.0038). In the elderly population defective stereopsis is a common finding in the absence of any other ocular morbidity. The finding was not associated with any symptoms. Impaired stereopsis may be due to age related decrease in cerebral function.