In a multi-centre trial the effect of indoor rehabilitation in case of bronchial asthma in childhood and adolescence was evaluated on a prospective basis in comparison to an ambulant group of patients. 195 children and adolescents aged between 8 and 16 suffering from bronchial asthma (grading of severity 3 and 4) were included in the trial. The rehabilitation group (RG) included 149 patients, whereas the out-patient reference group consisted of 46 patients. At the beginning of the trial (in the rehabilitation group about 14 days before rehabilitation started) and 12 months afterwards, the pulmonary function (FEV 1, peak flow and MEF50), asthma-related school day off, participation in school sport, asthma management and quality of life were recorded. 12 months after the indoor rehabilitation, the rehabilitation group had significantly better MEF50-values (P = 0.007) than the ambulant group. The rehabilitation group also had significantly better values (P < 0.01) with regard to the asthma management. Already at the beginning of the study both groups indicated a satisfactory participation in school sport with 3.5 hours a week which could not be increased further. The baseline values for asthma-related school day off and quality of life of the rehabilitation group were worse than those of the ambulant group. 12 months after rehabilitation, however, the values were significantly better (P < 0.01) compared to baseline and almost similar to the levels of the ambulant group. Significantly improvements with regard to MEF50, asthma management, school day off and quality of life could thus be achieved by indoor rehabilitation.