Incidence figures show that occupational asthma is increasing. It often takes a deteriorating course. Follow-up studies of workers suffering from the disease have uniformly reported persistence of symptoms over long periods, even among formerly exposed workers. New initiators of occupational asthma are continuously being reported. Still "old" agents, such as diisocyanates and flours, remain major causes. There seems to be some disconnection in the dialogue between the medical and the technical parties involved. For prevention, it is essential to ensure that important information not only reaches those who are responsible for designing and maintaining processes, but that it is presented in an intelligible form. Occupational asthma has become an important occupational disease that merits high priority. Recent achievements should facilitate preventive actions. However, prevention is a multidisciplinary enterprise needing the commitment of industrial hygienists and engineers, chemists, and allergologists, in addition to that of occupational health personnel.