Patients receiving standard prophylaxis treatment with ReFacto AF as determined by the inclusion criteria will be included in the study. During this observational study, patients diagnosed with severe hemophilia A, and starting or continuing prophylaxis with ReFacto AF as per local standard clinical care, will be observed for 12 months. Patients who received prophylaxis with another FVIII product and are scheduled to switch to ReFacto AF prophylaxis can also be enrolled. Physician decision to initiate or to continue ReFacto AF prophylaxis therapy will be independent and it will precede subjects' inclusion in the study. Also the physician decision to switch the prophylaxis with another FVIII product to ReFacto AF will be independent and it will precede subjects' inclusion in the study. Detailed information on hemophilia A history and previous hemophilia treatments will be collected at Baseline. The number of bleedings and their treatment, status of joints and the quality of life will be assessed at 3, 6, 9 and 12 months after ReFacto AF prophylaxis initiation.