Influx of polymorphonuclear leukocytes (PMNs) and monocytes (MNs) into pleural spaces was decreased in dimethyl sulfoxide (DMSO)-treated rabbits infected intrapleurally with Staphylococcus aurem. In addition, pleural fluids contained S. aureus longer and marked pleural thickening with fibrosis occurred in DMSO-treated rabbits. DMSO also inhibited stimulated locomotion of PMN and MN in vitro, suggesting that the aforementioned responses in vivo may have occurred because of DMSO-mediated inhibition of the locomotion of PMN and MN. © 1983 Plenum Publishing Corporation.