In the Netherlands comparable levels of sports-participation between persons with haemophilia and healthy controls have been reported. This raises the question if children with haemophilia under the currently available prophylaxis do reach comparable levels of physical fitness and health-related quality of life (HRQoL) as their healthy peers. The aim of this study was to investigate the level of physical fitness, functional ability and quality of life and to determine the feasibility to safely test the exercise capacity of boys with severe haemophilia A. Thirteen subjects participated in this study. Physical fitness was determined using the measurement of maximal oxygen uptake (VO2peak) attained during a graded maximal exercise test to volitional exhaustion. Joint health, physical activity levels and health-related quality of life (Haemo-Qol) were also measured. Mean VO2peak was 1.86+/-0.77 L min-1 (Z-score: -0.39+/-1.61) which was not significantly different from reference values. Relative VO2peak was 47.42+/-8.29 mL min-1 kg-1 (Z-score: -0.52+/-1.43), which did not differ significantly from reference values either. One boy suffered a joint bleeding one day after the test. Haemo-Qol scores in parents and children ranged from 3.2% to 36.7% (100% reflects poor outcome). Relationship between the child or parent reports of Haemo-QoL and both absolute and relative VO2peak ranged from R=0.00 and R=0.4. Exercise testing in children with severe haemophilia A was a safe procedure. Patients with severe haemophilia A with good joint health and no limitations of activities have comparable physical fitness and physical active lifestyle with healthy peers and good HRQoL.