Ticlopidine is a thienopyridine derivative which reduces the risk of reversible ischaemia and stroke in patients who have previously experienced a cerebral ischaemic episode. In comparison with aspirin, ticlopidine produced a significant reduction in the risk of stroke in a multicentre clinical trial involving more than 3000 patients with previous transient or persistent minor ischaemia, and was superior to placebo for the prevention of stroke recurrence in more than 1000 patients who had experienced a major thrombotic stroke. The cost-utility ratio for ticlopidine in comparison with aspirin was estimated to be $US31 200 to 55,000 per quality-adjusted life-year gained. Diarrhoea is the most common adverse event in ticlopidine recipients (20 to 22% incidence versus about 10% with placebo), although skin rash, nausea, dyspepsia, bleeding events, abnormal liver function and haematological disturbances were also observed in clinical trials. Severe neutropenia is the most serious event: this developed in 0.85% of patients receiving ticlopidine in 2 large clinical studies (n = 4098) but resolved after treatment withdrawal. Fatal neutropenia, although rare, has been reported in some patients receiving ticlopidine. Thus, ticlopidine is effective in reducing the risk of recurrent cerebral ischaemia and stroke. It appears to provide a gain over aspirin for the prevention of stroke after reversible ischaemia, particularly during the first year of treatment (when the risk of stroke is greatest), although further data on its absolute relative benefit would be useful. The extent to which ticlopidine is prescribed will probably depend on individual clinicians' perception of its risk/benefit and cost-effectiveness profiles. Ticlopidine is likely to be particularly useful for stroke prophylaxis in patients who do not tolerate aspirin or who have an ischaemic episode during aspirin treatment, and for the prevention of stroke recurrence in patients who have previously experienced a major stroke.