Physical fitness in a group of 49 stable asthmatic children was determined by an incremental exercise test. Thirty-one normal children served as a control group. The asthmatic children were divided into three groups. Group 1 was comprised of 16 children who actively participated in organized sports, Group 2 of 16 children who did not participate in organized sports but who engaged in free-play, and Group 3 of 17 children with a sedentary life-style who avoided even free-play. The results of cardiopulmonary evaluation before and after maximal incremental exercise testing have shown that Groups 1 and 2 behaved like the control group and their physical fitness was similar. Group 3 whose life-style was sedentary had poor physical fitness as compared to the other asthmatics and to the control group. This was the result of poor cardiovascular conditioning and was unrelated to the respiratory limitation. We conclude that poor physical fitness in asthmatic children is the result of a sedentary life-style and can be potentially normalized.