Interleukin 6 (IL6) secretion by blast cells derived from peripheral blood of patients with acute myelogenous leukemia (AML) was characterized. IL6 secretion showed a wide variation both when AML blasts were cultured in medium alone and in the presence of exogenous cytokines. The level of IL6 secretion was significantly correlated to secretion of other cytokines (IL1 alpha, IL1 beta, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, tumor necrosis factor alpha). IL1 beta, granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor and stem cell factor increased IL6 secretion, whereas IL4 caused decreased IL6 secretion together with increased release of IL1 receptor antagonist.