Evidence has previously been presented that monocytes and macrophages produce urokinase-type plasminogen activator. We have shown for the first time that human monocytes, when stimulated appropriately in vitro, can produce tissue type-plasminogen activator (t-PA) of 70 kD. Detection of t-PA mRNA was consistent with the biochemical and immunological characterization of t-PA produced by human monocytes.