In 218 men, who had minimal occupational exposure to dusts, fumes, temperature variability, or physical exercise, the relation between housing conditions throughout life and lung function was analysed. The number of years spend in dwellings without central heating was significantly inversely associated with the level of FEV1 and MMEF, and significantly directly associated with closing capacity in per cent of TLC, CC%. Significant dose-response relationships between smoking habits and FEV1, MMEF, CC% and slope of the alveolar plateau (phase III) were found, whereas closing volume, CV%, was only correlated to age. The association between dwelling conditions and ventilatory capacity was independent of smoking habits. Tobacco smoking, however, moderated the association in as much as it was strengthened after standardisation for tobacco consumption. These data support the hypothesis that poor dwelling conditions during childhood and adolescence are associated with development of peripheral airways disease and expiratory airflow obstruction at middle age, and that comparisons of lung function between different occupational categories are incomplete and may be misleading if lifelong housing conditions or other factors reflecting socio-economic status are not taken into consideration.