The observation of two clinical cases make possible an evaluation of the potential therapeutic activity of platelet function inhibitors in thrombotic thrombocytopenic purpura (TTP). In particular, the clinical and hematological effects of ticlopidine (TC), employed alone in two TTP patients, are reported. The mechanism of action of this peculiar antiplatelet drug is mainly represented by the inhibition of fibrinogen binding on the platelet surface. In the first patient, a 45-year-old female in whom plasma-exchange (PE) and corticosteroids (C) led to a partial remission (platelets 80 x 10(9)/l), treatment with TC at a dose of 750 mg/day was carried out, and after 6 weeks a normal platelet count was observed. A complete remission was maintained for 31+ months, even after reduction of the TC dose to 250 mg/day. In the second patient, an 18-year-old female affected by relapsing TTP, a complete remission obtained with PE and C was maintained for 19 months in concomitance with TC treatment, started at a dose of 750 mg/day and lowered to 250 mg/day. After 11 months of treatment at this low dosage there was a relapse (platelets 20 x 10(9)/l), but the increase of the TC dose to 750 mg/day in a few weeks induced a complete remission again. These data, in accord with a few other recent preliminary reports, suggest that TC, even alone, may play an interesting role in the management of TTP patients.