Three cases of boys were reported with severe hemophilia A [11 years, 5 years and 1 year old]. They all underwent central venous line [CVL] insertion for primary prophylaxis in the first and the third cases and for the induction of immune tolerance in the second case. In all cases, the CVL was a subcutaneous port-a-catheter and the CVL associated thrombosis was suspected because of malfunction of the port-a-catheter. In one of the boys, the port-a-catheter had been in place for 6 months and in the other 2 for over 3 years. In all three boys, there was no evidence of an underlying genetic predisposition to thrombosis, e.g., activated protein C [APC] resistance. All of them underwent bilateral arm venogram which confirmed the presence of CVL- related thrombosis. Thrombi were located in the left subclavian and brachiocephalic veins in the first and second cases, and in the left brachiocephalic vein in the third case. These findings were unexpected as historically hemophiliacs are through to be protected from thrombosis by virtue of anticoagulation nature of their disease. Based on this observation, it is strongly recommend that physicians caring for hemophiliacs to critically should evaluate the risks and benefits related to CVL insertion.