An asthma data register which collects annually certain data from all known local asthmatic children has been presented. The data register is utilized to make a two-page print-out for every patient, and statistics of the whole material. These data make the continuous surveillance and guidance of the patients possible. The easy-to-use and accurate data material has contributed to rationalization of routine work in an asthma clinic. Team work has also improved because the uniform data material enables various workers to quickly pick out a specific problem from the whole material. The cost, $ 2 to 3 per patient per year, is low compared with the immediate benefit. Indirect benefit is to be expected because the system helps to investigate the problems of asthmatic children.