In a random sample of 648 adults (18-70 years), representing 95,836 people by age and sex, the prevalence of the above mentioned diseases was assessed. The chi 2-test revealed that the sample of examined subjects did not differ significantly from the distribution of the population as regards age and sex. The prevalence of bronchial asthma was 2.0%, of chronic bronchitis 16.3%, pollen rhinitis 4.5% and non-seasonal rhinitis 4.9%. In asthma the immunological type of the disease predominated markedly. Bronchial hyperreactivity after inhaled histamine was almost five time higher in asthma than in bronchitis (100% and 22.5%).