The pulmonary function of 24 Norwegian divers who had participated in a deep saturation dive to pressures of 3.1-4.6 MPa was reevaluated one and four years later. Twenty-eight divers performing ordinary saturation diving to pressures of 0.8-1.6 MPa and followed over a three-year period served as referents. A significant reduction in forced expiratory volume in 1 s (FEV1.0) of 210 (SD 84) ml (P < 0.001) occurred the first year after the dive. Thereafter the annual reduction in FEV1.0 was 28 (SD 62) ml.year-1; this value did not differ from the 35 (SD 80) ml.year-1 of the referents. The forced midexpiratory flow rate and forced expiratory flow rates at low lung volumes were also significantly reduced one year after the deep dive, and the closing volume was increased. No significant changes occurred in forced vital capacity. The results agree with those of cross-sectional studies on divers' lung function and indicate the development of airflow limitation in relation to diving exposure.