Patients with haemophilia A and inhibitors are at high risk for severe bleeding, progression of joint disease and deterioration of health-related quality of life (HRQoL). To determine the impact of prophylaxis with an activated prothrombin complex concentrate (aPCC) on HRQoL, HRQoL was assessed using the Short-Form (SF)-36 Health Survey and the EQ-5D questionnaire in subjects 14years participating in a prospective, randomized, crossover study comparing 6months of aPCC prophylaxis with 6months of on-demand therapy. Eighteen of 19 patients completed the survey or questionnaire before and after the on-demand therapy and prophylaxis periods. A general trend towards improved HRQoL after prophylaxis was observed for the 18 evaluable patients in all SF-36 dimensions except for vitality/energy and physical functioning. After prophylaxis, good responders,' defined as patients experiencing 50% reduction in bleeding, exhibited statistically and clinically significant differences in the physical component score (P=0.021), role - physical (P=0.042), bodily pain (P=0.015), and social functioning (P=0.036). Similarly, the EQ-5D health profile showed a trend towards improvement after prophylaxis in all evaluable patients. Among the good responders, improvements did not differ from those observed after on-demand treatment. EQ visual analogue scale values were slightly improved following prophylaxis for all evaluable patients and the EQ-5D utility index improved in the good responders only. During prophylaxis, patients missed significantly fewer days from school or work because of bleeding than during on-demand treatment (P=0.01). In conclusion, by significantly reducing bleeding frequency in good responders, aPCC prophylaxis improved HRQoL compared with on-demand treatment.