This study evaluated polymorphonuclear leukocyte (PMN) involvement in translocation of dust to bronchial lymph nodes after deposition of dust in the lungs of control and neutropenic F344/N rats. Rats were rendered neutropenic with an intraperitoneal (IP) injection of anti-rat PMN antiserum (APA); control rats were injected IP with 0.9% saline solution. Eighteen hours after IP injections, control and APA-treated rats were instilled intratracheally with 5 x 10(8) microspheres suspended in 0.9% saline solution, which caused an influx of PMNs into the pulmonary airspaces of control rats, but not of APA-treated rats. One day postinstillation (PI), 77.2% of the microspheres recovered in bronchoalveolar lavage fluid (BALF) from control rats were associated with pulmonary alveolar macrophages (PAMs) and 18.8% with PMNs; 4.0% were free. In BALF from the APA-treated rats, 66.3% of the microspheres were associated with PAMs and 0.3% with PMNs; 36.3% were free. Two days PI, about 95% of the microspheres in BALF from control and APA-treated rats were associated with PAMs; by 4 and 7 days PI, essentially 100% were with PAMs. Amounts of microspheres translocated to bronchial lymph nodes of control rats were four fold less than in the APA-treated rats on days 2, 4, and 7 PI (p < .05). The results suggest that PMNs in pulmonary airspaces of F344/N rats phagocytize dust and thereby interfere with the mechanism(s) involved in dust penetration into the pulmonary interstitium.