Information on the prognosis of patients with transient ischaemic attack or moderately disabling ischaemic stroke associated with bilateral internal carotid artery (ICA) occlusion is scarce. We prospectively studied 57 consecutive patients (46 men; mean age 60 +/- 9 years) with bilateral ICA occlusion who had presented with unilateral transient or moderately disabling cerebral or retinal ischaemic symptoms. We determined the long-term risk of recurrent ischaemic stroke and the composite outcome of stroke, myocardial infarction or vascular death. Four patients had a recurrent ischaemic stroke during a mean follow-up of 5.9 years, resulting in an annual stroke rate of 1.2% (95% confidence interval (CI) 0.3-3.1). Risk factors for recurrent ischaemic stroke could not be identified. Eighteen patients suffered a stroke, myocardial infarction or vascular death, resulting in an annual rate for major vascular events of 5.3% (95% CI 3.1-8.3). Age and a history of ischaemic heart disease were significant risk factors for future vascular events. Patients with transient or moderately disabling symptoms of cerebral or retinal ischaemia associated with bilateral ICA occlusion have a relatively low risk of recurrent ischaemic stroke. Although this study was not designed to compare conservative treatment with surgical intervention, the favourable outcome suggests that a policy of medical therapy and control of risk factors may be justified in these patients.