The efficacy of aspirin in daily doses of 300 mg and more as secondary prophylaxis after cerebrovascular events is well established. Since much lower doses of aspirin can inhibit platelet function, and carry a lower risk of adverse effects, the Swedish Aspirin Low-dose Trial (SALT) was set up to study the efficacy of 75 mg aspirin daily in prevention of stroke and death after transient ischaemic attack (TIA) or minor stroke. 1360 patients entered the study 1-4 months after the qualifying event: 676 were randomly assigned to aspirin treatment and 684 to placebo treatment. The median duration of follow-up was 32 months. Compared with the placebo group, the aspirin group showed a reduction of 18% in the risk of primary outcome events (stroke or death; relative risk 0.82, 95% confidence interval 0.67-0.99; log-rank analysis p = 0.02), and reductions of 16-20% in the risks of secondary outcome events (stroke; stroke or two or more TIAs within a week of each other necessitating a change of treatment; or myocardial infarction). Adverse drug effects were reported by 147 aspirin-treated and 123 placebo-treated patients Gastrointestinal side-effects were only slightly more common in the aspirin-treated patients, but that group had a significant excess of bleeding episodes (p = 0.04). Thus, we have found that a low dose (75 mg/day) of aspirin significantly reduces the risk of stroke or death in patients with cerebrovascular ischaemic events.