In four ovarian cancer patients with malignant ascites, 10 KE of OK-432 was intraperitoneally administered four times every other day for priming, and 40 KE of OK-432 in a single dose by the same route on day 13 for triggering. The changes in peripheral blood monocytes and intraperitoneal macrophages and the production of tumor necrosis factor (TNF) by peripheral blood mononuclear cells (PBMC) and ascitic lymphoid cells (ALC) were examined. In two of the four patients in whom TNF was induced in the ascites, the TNF production by PBMC and ALC was noted during priming, and after triggering, an increase in both the number of intraperitoneal macrophages and the TNF production by ALC was noted. In two other patients in whom TNF was not detected in the ascites, the ratio of intraperitoneal macrophages to ALC did not change throughout the whole period, and the TNF production by ALC was not augmented. These findings suggest that the priming administration of OK-432 can induce both intraperitoneal macrophages and peripheral blood monocytes into a primed state, and the triggering administration of OK-432 can increase the number of intraperitoneal OK-432-primed macrophages and induce TNF release from these cells.