BACKGROUND There at present exists marked controversy as to the possible greater efficacy of ticlopidine as opposed to aspirin in brain ischaemia secondary prophylaxis. In our study we compare the efficacy and safety of antiaggregant treatment with ticlopidine as opposed to aspirin in a group of 310 patients admitted to the 'Hospital Mutua de Terrassa' between the years 1990 and 1994. RESULTS In the group of patients treated with ticlopidine we found a larger number of new cerebrovascular incidents (p = 0.02) and peripheral vascular incidents (p = 0.01). New cerebrovascular incidents were more frequent in males (p = 0.03), in those patients with substantiated infarct (p = 0.02) and in patients with ischaemia in the carotidal region (p = 0.04). On the other hand, the group of patients treated with ticlopidine presented more secondary effects than the group treated with aspirin at the digestive (p < 0.001) and haematologic (p < 0.001) levels. The most frequent digestive secondary effects were diarrhoea (p < 0.001) and hepatopathy (p = 0.02); abnormalities in the leucocyte count were more frequent in patients treated with ticlopidine (p < 0.001), neutropenia being found in 0.8% of cases. CONCLUSIONS In the patients we studied ticlopidine was less efficacious than aspirin in the secondary prophylaxis of new vascular incidents (both cerebrovascular and peripheral vascular) and also presented a greater incidence of secondary (digestive and haematological) effects.