The authors studied and determined a correlation between the distribution of particle size in induced sputum and pulmonary function tests among 54 foundry workers, of whom 34 had been exposed to a variety of metals. Sputum was induced with an ultrasonic nebulizer and processed by conventional methods; a particle scanner was used to measure particle size. All participants underwent spirometry to measure their flow rates. There were significant differences between the exposed and nonexposed groups with respect to the proportion of particles with diameters greater than 2 microm and with diameters greater than 5 microm. A positive correlation was found between the proportion of particles greater than 5 microm in diameter and the ratio of forced expiratory volume in 1 sec (FEV1.0) to forced vital capacity (FVC) (i.e., FEV1.0/FVC) for all 54 workers, and there was a significant correlation for non-smokers. Correlations by work categories revealed a significant negative correlation among casting workers between particles with diameters greater than 5 microm and percentage of FVC. These findings indicate the value of measuring particle size in induced-sputum specimens as a tool for differentiating between exposed and nonexposed workers. Also indicated was a tendency toward a restrictive pattern in pulmonary function tests among workers who had exposure to higher percentages of large particles.