OBJECTIVE--To study the association between allergic diseases (eczema, allergic rhino-conjunctivitis, and asthma), dental health, and the socioeconomic situation of Swedish teenagers. DESIGN--Cross-sectional survey with a questionnaire for allergic symptoms and parents' occupation (for socioeconomic classification); current dental status from the Public Dental Service. Bronchial reversibility test. Telephone inquiry of asthma cases. SETTING--Primary care and a school in the centre of a middle-sized Swedish town (approx. 80,000 inhabitants). PARTICIPANTS--137 pupils of both sexes, 13-15 years old. MAIN OUTCOME MEASURES--Number of reported cases with allergic disease and outcome of bronchial reversibility test in relation to social class. Number of validated cases of asthma. Number of filled tooth surfaces in healthy and diseased cases. RESULTS--Socioeconomic situation was found to associate with dental health, i.e. more fillings in lower social classes (P = 0.01), and with allergic disease, i.e. asthma and rhino-conjunctivitis (P = 0.05). Individuals from the upper social classes seemed prone to overreport asthmatic symptoms, whereas teenagers in the lower classes did the opposite, as indicated by five cases of pathologic values after bronchial reversibility tests in individuals who did not report asthmatic symptoms. CONCLUSION--The study indicates that socioeconomic situation associates significantly with both dental health and allergic disease. No association was found between dental health and allergic diseases.