Proposed guidelines for the diagnosis of transient ischaemic attack (TIA) involve interpretation of symptoms, so it can be very difficult to distinguish a TIA from other disorders, such as migraine, epilepsy, syncope, or neurosis. Atypical cerebral and visual events may be classified as TIA. To see whether TIA or stroke patients with atypical cerebral or visual symptoms are at high or low risk of cardiac complications, we prospectively followed 572 patients (entered into the Dutch multicentre TIA trial) with a diagnosis of TIA or minor ischaemic stroke, but whose symptoms did not fully accord with internationally accepted criteria. We compared their outcome with that of 2555 other TIA or stroke patients in the trial, who had unequivocal symptoms; all patients were treated with aspirin. During mean follow-up of 2.6 years the risk of a major vascular event did not differ between the groups (14.5% in patients with atypical symptoms vs 15.1% of patients with typical attacks). Patients with atypical attacks had a lower risk of stroke (5.6% vs 9.4%, hazard ratio 0.6, 95% confidence interval 0.4-0.9) and a higher risk of a major cardiac event (8.4% vs 5.9%, 1.4, 1.0-2.0) than did patients with typical attacks. These differences could not be explained by differences in cardiac risk factors, and were independent of minor discrepancies in baseline characteristics between the groups. A heavy or tired feeling in one or two limbs was the only atypical symptom associated with cerebral rather than cardiac events (ratio cardiac/cerebral events 0.8). For all other atypical symptoms cardiac events were about twice as common as cerebral events (range 1.3-2.5). Our findings suggest that TIA or minor stroke patients with atypical symptoms may have symptomatic heart disease, especially cardiac arrhythmia.