Background: Glanzmann’s Thrombasthenia (GT) is a rare autosomal, recessive, bleeding syndrome. The main aim of this study was to investigate the relationship between symptoms, bleeding severity, and gender and subtypes of GT by platelet immunophenotyping.Materials and Methods: Ninety five patients with Glanzmann’s Thrombasthenia (GT) were assessed for the expression of GPIIb-IIIa on the platelet surface using flow cytometry, to determine the most common GT subtypes among Iranian patients. We also evaluated the severity of bleeding phenotype, and classified them as mild, moderate, or severe bleeders.Results: On the basis of their platelet GPIIb-IIIa levels, 73 patients (77%) were classified as type I, 16 patients (17%) as type II, and 6 patients (6%) as type III. Historically, 15 of 95 patients had experienced minor bleeding, 32 reported clinically significant bleeding, and 48 patients had suffered severe bleeding. Thirty eight patients had needed packed red blood cell transfusion. However, no significant correlation was found between bleeding severity and subtypes of GT (p >0.05).Conclusion: Our study showed that there was no correlation between quantitative changes in the surface expression of platelet membrane glycoproteins, and the intensity and frequency of bleeding episodes in patients with GT.