Background and Methods: A single centre study including 52 German patients aged ≥16 years with severe haemophilia A was performed to compare the amount of clotting factor and outcome between on-demand therapy (26 patients) and continuous prophylaxis (26 patients) over 1 year. Results: Prophylaxis reduced the number of bleeds significantly. Compared to on-demand treatment (20.5 ± 3.0 bleeds/year/patient), under prophylaxis 7.8 ± 1.3 bleeds/year/patient were observed. Joint bleeds were reduced from 12.2 ± 1.5 to 4.7 ± 1.0/year/ patient. In the on-demand group 38% of the patients suffered from more than 2 bleeds/month, whereas in the prophylaxis group no patient was found with more than 2 bleeds/month. Mean annual factor VIII (FVIII) consumption increased from 767 ± 110 IU/kg body weight under on-demand treatment to 2,841 ± 341 IU/kg body weight under continuous prophylaxis, displaying a nearly fourfold increase in FVIII consumption. Furthermore, prophylaxis implies a more than four-fold increase in treatment days which escalated from a mean weekly injection rate of 0.56 ± 0.08 FVIII injections/week when bleeds were treated on demand to 2.52 ± 0.30 FVIII injections/week during prophylaxis. Conclusion: Even though the results reflect a benefit also for prophylactically treated patients regarding their bleeding frequency, one has to take into account a substantial increase of the costs for coagulation concentrates when all patients with severe haemophilia A switch to continuous prophylaxis.