A comparative study of the prevention of recurrences of cerebral transient ischemic attacks during a 6-month observation period was conducted in 73 patients treated with a combination of acetylsalicylic acid and dipyridamole (ASAD, 1,050 mg + 150 mg/day) and in 65 patients treated with pentoxifylline (PTX 1,200 mg/day, Trental 400 t.d.s.). The patients were randomly assigned to the treatments. Risk factor analysis showed high prevalence of arterial hypertension, hyperlipidemia and smoking in these patients. The two groups were matched in terms of age, sex, blood pressure and site of TIA origin (carotid 63% in the ASAD, 65% in the PTX group). 23 ASAD patients and 9 PTX patients suffered a recurrence. There were 4 nonfatal stroke events with ASAD and 2 with PTX. 80 recurrent TIAs were recorded in 19 ASAD patients compared with 19 such episodes in 9 PTX subjects. The morbidity rates (life table analysis) were significantly lower (p less than 0.05) in the PTX group. The results of the study point to a preventive effect of PTX in terms of the reduction in TIA recurrences.