Tumour necrosis factor (TNF) alpha, interleukin (IL) 1 beta, IL-6 and IL-8 are thought to play a central role in the pathophysiology of sepsis but their role in acute pancreatitis is unknown. In the present study, monocytes were isolated from the peripheral blood of 26 patients with moderate or severe acute pancreatitis without biliary sepsis. Secretion of these cytokines in vitro was measured at intervals during the first week of illness. Sixteen patients developed systemic complications. Peak TNF-alpha secretion was significantly higher in patients who developed systemic complications (median (interquartile range (i.q.r.)) 18.5 (5.5-28.5) ng/ml) than in those with an uncomplicated course (3.7 (2.3-6.4) ng/ml, P < 0.01). Similarly, peak IL-6 and peak IL-8 secretion were significantly higher in the complicated group (IL-6: complicated median (i.q.r.) 48.9 (12.1-71.0) ng/ml, uncomplicated 16.3 (14.2-37.9) ng/ml, P < 0.05; IL-8: complicated 748 (643-901) ng/ml, uncomplicated 608 (496-749) ng/ml), P < 0.05). No significant difference in peak IL-1 beta secretion was observed between the two groups. Systemic complications of acute pancreatitis are associated with a significant increase in monocyte secretion of TNF-alpha, IL-6 and IL-8 suggesting that, as in sepsis, these cytokines play a central role in the pathophysiology of the disease.