The role of the platelet glycoprotein (GP) IIIa polymorphism HPA 1b (Pl^A2) in the risk of arterial thrombosis is controversial. We investigated the effect of the 1b allele on platelet fibrinogen binding by flow cytometry. Samples from 35 healthy platelet and plasma donors possessing the 1b allele were compared with 35 1a/1a donors. We found no allele‐dependent difference in percentage of platelets binding fibrinogen (P  =  0.6), nor in mean cell fluorescence (P  =  0.3) following stimulation with ADP. These results render it unlikely that any relationship between the 1b polymorphism and arterial thrombosis is mediated by a significant effect on fibrinogen binding.