A total of 2435 patients with transient ischaemic attack or minor ischaemic stroke were entered into the UK-TIA aspirin trial and randomised to treatment with aspirin 1200 mg/day, aspirin 300 mg/day, or placebo. At a single point in time during the trial patients were examined ophthalmoscopically for evidence of cataracts. The length of time that each patient had been participating in the trial at the time of ophthalmic examination varied from 1 to 5 years. The prevalence of cataracts was similar in patients allocated aspirin and patients allocated placebo irrespective of the length of time that they had been in the trial. These findings suggest that aspirin taken in a dose of 300 to 1200 mg daily for a few years does not prevent cataracts.