Sixty-two patients with gynecological disease, who were treated with sizofiran (SPG) intramuscularly before laparotomy or with recombinant interferon gamma (IFN) intraperitoneally on the day of the laparotomy, were studied to investigate the change on the number and function of peritoneal macrophages (PM) obtained by peritoneal washing on the day and on the 1st and 4th days after the laparotomy. SPG significantly increased the number of PM by the 1st day, and IFN by the 4th day (p less than 0.05). However, IL-1 and IFN-gamma secretion by PM were not activated by SPG or IFN treatment, respectively. When patients were treated with these two agents simultaneously, the number of PM was significantly increased by both the 1st and the 4th day (p less than 0.05), and IL-1 and IFN-gamma secretion by PM were also significantly activated by the 1st day (p less than 0.05). These data suggest that SPG and IFN had a synergistic effect on increasing the number of PM and on activating the secretion of cytokines by PM, and that the priming with SPG played an important role in the activation of PM function by IFN.