In ischaemic stroke, thrombolytic drugs speed the recanalisation of intracerebral arteries. The effects of aspirin are not known. A trial was conducted to determine whether, separately or together, streptokinase and aspirin have clinical benefits in acute ischaemic stroke similar to those in acute myocardial infarction. 622 patients with acute ischaemic stroke within 6 hours of symptom onset were randomised with a 2 x 2 factorial design to (i) a 1-hour intravenous infusion of 1.5 MU streptokinase, (ii) 300 mg/day buffered aspirin for 10 days, (iii) both active treatments, or (iv) neither. Early results raised a question whether the trial should be continued. Streptokinase (alone or with aspirin) was associated with an excess of 10-day case fatality (odds ratio 2.7; 95% confidence interval 1.7-4.3; 2p < 0.00001). Of the four groups randomised, only patients allocated to streptokinase plus aspirin had a significantly higher risk of early death than those given neither streptokinase nor aspirin (odds ratio 3.5; 95% CI 1.9-6.5; 2p < 0.00001). Streptokinase (alone or with aspirin) and aspirin (alone or with streptokinase) reduced, albeit not significantly, the incidence of combined six-month case fatality and severe disability: odds ratio for streptokinase 0.9 (95% CI 0.7-1.3) and odds ratio for aspirin 0.9 (95% CI 0.6-1.3). The risk of early death with thrombolytic treatments should be weighed against the potential benefit of a marginal reduction of severe disability after the first six months.