Effects of lipopolysaccharides (LPS) on the production of chemotactic lymphokines for eosinophils and monocytes (ECF and MCF) from antigen- or mitogen-stimulated T cells were examined. Supernatants from monocytes stimulated with various LPS regulated concanavalin A (Con A)- and purified protein derivative (PPD)-induced ECF or MCF production. The regulation varied with LPS used for monocyte stimulation. The supernatant from monocytes stimulated with LPS from Escherichia coli, J-5 strain, selectively potentiated ECF production, whereas that from Salmonella minesota potentiated MCF production. In contrast, supernatant from monocytes stimulated with LPS from Salmonella typhimurium potentiated both ECF and MCF production, whereas that from Vibrio cholerae failed to potentiate production. The supernatants from monocytes stimulated with lipid A of S. typhimurium, S. minesota, and E. coli, however, failed to potentiate ECF and MCF production. The potentiating activity for each lymphokine was recovered from fractions ranging in molecular weight between 10 and 20 kD. Further purification with isoelectric electrophoresis revealed that the potentiating activity for the production of chemotactic lymphokine for eosinophils has a pI value of about 4-5, and that the activity for MCF production is detected in two fractions of pI about 5-6, and 7-8. Macrophage lineage cell line cells, such as THP-1 and U-937, also release similar factors after differential stimulation.