In 1990, 1530 active Swiss athletes of national or international level (53% response rate) answered a questionnaire on allergies, hay fever and respiratory symptoms during or after physical effort. Compared with 1986, the prevalence of allergies among these athletes had increased from 14.7 to 18%, and of hay fever from 16.8 to 19.7%. The prevalence of respiratory symptoms was 12.1 in 1990, compared with 7.1% in 1986. Smoking was less frequent than in 1986 (7.1% against 12%). There was a significant correlation between the reported allergies and respiratory symptoms, but none between respiratory symptoms and smoking or frequency of consultations at a physician's office. The examination of 104 athletes complaining of respiratory symptoms on 10 minutes ergometry showed a decrease of FEV1 of 10% or more in 21%. Exercise induced asthma (EIA) is not as frequent as suspected in other publications. 25% of the sportsmen examined showed a cutaneous allergy to one or more of the six most frequent inhalative allergens. The typical history of dyspnea, wheezing or coughing after exercise, possibly combined with a feeling of tightness of the chest or the larynx, and the number of positive allergy skin test reactions, correlated with the decrease in FEV1 after exercise. A considerable percentage of these athletes do not treat their respiratory symptoms or ask for professional help. In medical treatment, attention must be paid to doping regulations. IOC accepts the use of salbutamol, terbutaline, orciprenaline and Cromoglycic acid in the treatment of asthma. Corticosteroids by inhalation are accepted but intramuscular injection is forbidden.(ABSTRACT TRUNCATED AT 250 WORDS)