The platelet membrane glycoprotein (GP) IIb/IIIa, GPIX were detected by immunogold assay and flow cytometry, respectively, in two cases of Glannzmann's thrombasthenia (GT). The immunogold assay showed that the GP IIb/IIIa gold granules in GT were decreased obviously, compared with that in normal controls. Flow cytometry results showed that GP IIb/IIIa in two cases of GT was 0.1% and 0.5% of normal control, respectively. While GPIX showed no difference between the GT and normal control. The patients' father showed no bleeding symptoms, whose GP IIb/IIIa accounted for 36.99% of normal control. The experiment results suggested that flow cytometry is a quick, simple and sensitive method for the diagnosis of GP disorders.