The effect of intermittent exposure to hyperbaric oxygen over a long period of time was evaluated in 65 subjects. Pulmonary ventilation and diffusion capacities were measured in 65 divers as well as in 67 control subjects. No significant difference was found (P < 0.05) in any of the measured respiratory parameters between the divers and the controls in spite of the diver's long-term occupational exposure to hyperbaric oxygen.