Effects of 2-hr exposure to sulfuric acid (H2SO4) on pulmonary functions in male nonsmokers were examined. Subjects were exposed to air and 233, 418 and 939 micrograms/cu m H2SO4 at 22C DB/55% RH or air and 314, 600 and 1107 micrograms/cu m H2SO4 at 35C DB/85% RH. Mass media diameter was 0.92 micrometer, a sequence of 20-min exercise (VE of 30 1/min) and 20-min rest was repeated three times during each exposure. Pulmonary functions (forced vital capacity, lung volumes, maximum voluntary ventilation, airway resistance, total gas volume) were measured pre- and post-exposure. In addition, forced vital capacity was determined following each exercise period. No significant changes in pulmonary functions were observed for H2SO4 exposure. An increased prevalence of symptoms, such as cough, dry throat or throat irritation, was observed for H2SO4 exposure, suggesting that H2SO4 may have caused some pulmonary irritation though not sufficient to induce functional changes. It was concluded that 2-hr exposure, with intermittant exercise, to H2SO4 in the one micrometer size range and in concentrations up to 1100 micrograms/cu m had relatively minor effects on the pulmonary system.