The local release of human neutrophil lipocalin, considered to be highly specific for neutrophil granulocyte activation, and interleukin-8 and tumor necrosis factor-alpha were studied in 11 patients with distal ulcerative colitis and proctitis before and during treatment with steroid enemas. A rectal perfusion technique for sampling and specific immunoassays for analysis were used. In responders (N = 8) the concentrations of all proteins decreased during the study. There was a close correlation between human neutrophil lipocalin concentrations and treatment response. Tumor necrosis factor-alpha showed an initial decline in concentrations irrespective of treatment outcome and preceded the decline of human neutrophil lipocalin and interleukin-8. We conclude that decreased neutrophil degranulation is correlated with treatment outcome. Furthermore, an important role of tumor necrosis factor-alpha in the process of stimulating neutrophil activation and degranulation in ulcerative colitis is suggested.