A study was conducted to determine if acute respiratory effects, measured in terms of changes in forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and maximal expiratory flow rate at 50% of forced vital capacity (.ovrhdot.Vmax50), were related to exposure to diesel emissions in coal miners. Coal miners (60) exposed to diesel emissions and miners (90) not exposed were tested before and after a work shift for ventilatory function changes. Significant work shift decrements in ventilatory function occurred in miners in both groups who smoked cigarettes, but there were no significant differences in the ventilatory function changes between miners exposed to diesel emissions and those not exposed in the aggregate or under control by smoking status.