Male Sprague-Dawley rats were exposed to 0.1, 1.0, or 3.0 ppm acrolein or filtered air 6 h/day, 5 days/week for 3 weeks. Rats were tested one day following the last exposure and exhibited no change in pulmonary clearance of inhaled (35)S-labeled Klebsiella pneumoniae at any acrolein concentration. Decreased numbers of peritoneal cells were obtained from exposed rats while the number of cells lavaged from the lungs was unchanged. Macrophages of acrolein-exposed rats had altered phagocytic and enzymatic patterns as compared to macrophages from animals breathing filtered air. However, these changes had no apparent effect on macrophage killing of inhaled bacteria and were therefore probably not indicative of extreme chemical toxicity. (Copyright (c) Elsevier Science Publishers B.V. (Biomedical Division) 1986.)