The authors present data on the natural course of childhood bronchial asthma. They made a follow-up on 441 formerly asthmatic patients after the age of 14 years. The follow-up was based on questionnaires accompanied with personal interviews, physical examination, etc. The disease began in 167 (38%) patients before the age of 2; at the 'end' of childhood, at the age of 14, 34% were still asthmatic. In young adult age symptoms recurred in some cases and at the age of 26, 43% of the patients showed asthmatic complaints. The frequency of asthmatic attacks was significantly less in the young adults compared with that of childhood. Death occurred in 5 former patients, but only 2 of them died as a consequence of asthmatic disease. The authors constructed a diagram on the natural course of childhood asthma and show the practical use of this curve.