The purpose of this study was to monitor platelet activation by following alpha IIb beta 3 integrin (GpIIb/IIIa complex or CD41/CD61) on the platelet surface by flow cytometry (FCM) analysis using workshop mAbs. The results obtained with the mAbs showed increased expression of the GpIIb/IIIa complex (about 40%) on the platelet membrane surface under thrombin stimulation.