In the Oxfordshire Community Stroke Project 14 patients were notified with lone bilateral blindness, defined as rapid onset of dimming or loss of vision over all of both visual fields simultaneously, lasting under 24 hours, without associated symptoms of focal cerebral ischaemia, epilepsy, or reduction in consciousness. The age of these patients was close to that of the 184 patients who presented with transient ischaemic attacks and they had a similar high prevalence of vascular risk factors. During a mean follow-up of 2.4 years, 5 of the 14 had a first-ever stroke (0.31 expected). In view of their 16 times (95% CI 7-39 times) excess risk of stroke such patients should be included, for practical purposes, under the diagnostic heading of transient ischaemic attack.