Increasingly, economic aspects become important in public health which makes necessary the quantification to economical and operational efficiency. One of the instruments applied in this process is cost-benefit-analysis, comparing preventive, curative and rehabilitative services under the aspect of cost and benefit and effectiveness. In this context, we have evaluated a project of ambulant training of asthmatic children and of their parents. We included 142 affected children and their parents, who were trained in the offices of 24 physicians. Evaluation was done with a questionnaire in which data were collected on asthma-management, on quality of life, and on cost-effectiveness. We looked at the year before starting the training and on the year after completion of the training. Treatment costs were decreased by training, life quality improved. Thus, ambulant training of asthmatic children and of their family is a useful and efficient part of preventive rehabilitation.