We prospectively measured the concentrations of immunoreactive tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6) in the serum and ascitic fluid of 14 alcoholic cirrhotic patients with spontaneous bacterial peritonitis (SBP) and 16 alcoholic cirrhotic patients with sterile ascitic fluid. TNF-alpha levels in ascitic fluid were significantly higher for the patients with SBP: 399.57 +/- 129.23 pg/mL vs. 35.76 +/- 5.57 pg/mL (P < .001). IL-6 levels in ascitic fluid were also significantly higher for the patients with SBP: 170,713 +/- 57,109 ng/mL vs. 5,414 +/- 973 ng/mL (P < .001). By contrast, serum levels of TNF-alpha and IL-6 were just slightly more elevated than normal values. The concentration of IL-1 in the ascitic fluid of all patients was elevated, but there was no difference between patients with SBP or sterile ascites in this respect. In the patients with SBP, levels of TNF-alpha and IL-6 in ascitic fluid decreased during the first 48 hours of antibiotic treatment. Our results suggest that measurements of TNF-alpha and IL-6 in ascitic fluid may become useful markers both for the diagnosis of SBP and for monitoring the treatment of cirrhotic patients.