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Cells of the myelomonocytic leukemia cell line RC-2A were studied for their ability to synthesize clotting-promoting and fibrinolytic factors. The cells were observed to generate procoagulant activity (PCA) in readily measurable quantities. Incubation of RC-2A cells with phorbol myristate acetate (PMA; 3 ng/ml) or phytohemagglutinin (PHA, 10 micrograms/ml) for 18 h resulted in a 4-5-fold increase in PCA relative to unstimulated control. The PCA of RC-2A cells was tissue factor-like in that it was dependent on factor VII but not on factors VIII or IX. RC-2A cells also produced plasminogen activator (PA). Secreted PA was approximately 70% of the PA of an identical number of human monocyte-derived macrophages; fresh isolated monocytes synthesized virtually no PA. Compared to macrophages, RC-2A cells secreted less or no PA-inhibitors. Lysates of RC-2A cells contained over three times more PA than lysed macrophages. Stimulation of the cells with lectins (PHA, concanavalin A) or PMA was followed by a modest (2-3-fold) increase in PA. Enzyme immunoassay with antibodies to urokinase (u-PA) or tissue-type PA (t-PA) identified the RC-2A plasminogen activator as being of urokinase type.