Antiplatelet therapy reduces the rate of complications of coronary angioplasty. Ticlopidine, in addition to acetyl salicytic acid (ASA), improves the results after coronary stenting, but early complications still occur. Ticlopidine given in the standard way has a slow onset of action. Eighteen ASA-treated stable coronary patients were randomized to standard ticlopidine treatment (250 mg twice daily) or to a loading dose of 1500 mg followed by 250 mg twice daily. After one day, standard treatment had a very modest antiplatelet effect, as assessed by ADP-induced platelet fibrinogen binding, whereas the loading dose resulted in a considerably better platelet inhibition; relative inhibition, 5.6-10.6 vs. 24.9-35.3% (p<0.005) with final ADP concentrations 3 and 0.6 microM, respectively. It is possible that a loading dose of ticlopidine, given the day before the procedure, might reduce the complications related to angioplasty and stenting.