The cytokine cascade which is triggered by severe sepsis may contribute to progressive organ dysfunction and death from sepsis. This cascade may be accentuated by surgery for sepsis and pre-treatment with cytokine blockers could possibly ameliorate the response. This prospective controlled study determined the effect of surgery in 11 haemodynamically stable patients undergoing laparotomy for intra-abdominal sepsis. Serum levels of endotoxin, IL-1, IL-6, IL-8 and TNF-alpha were determined; blood cultures, features of systemic inflammatory response, and organ dysfunction were monitored over the peri-operative period. There was considerable variation in the serum cytokine levels. The preoperative IL-6 levels were significantly elevated in the septic patients and a threefold increase in IL-6 levels occurred in both groups postoperatively. An increase in TNF-alpha did not achieve significance because of high levels in control patients with cancer. Cytokine release which occurs during abdominal surgery is increased in patients with intra-abdominal sepsis.