To study the contribution of phagocytosis to the development of acute lung injury, latex particles (2 x 10(9)/kg; mean diameter, 2.84 microns) were injected intravenously or intra-arterially into guinea pigs. 125I-labelled albumin was injected to estimate the degree of lung injury, and 51Cr-labelled red blood cells were injected to correct for blood contamination in the samples. A control group was given saline. Four hours after the injections, the animals were killed, bronchoalveolar lavage was done, and the lungs were examined histopathologically. Animals that had received intravenous and intra-arterial injections of latex particles had more lung water and more pulmonary albumin leakage than animals that had received saline. Histopathological examination revealed massive accumulation of latex in the reticuloendothelial system. These findings suggest that the phagocytic process in the reticuloendothelial system plays a role in the development of lung injury in guinea pigs.