Idiopathic membranous glomerulonephritis (iMGN) has previously been shown to be associated with urinary excretion of terminal complement complexes while increased urinary levels of cytokines have been reported in mesangial proliferative glomerulonephritis. In the present cross-sectional study urinary excretion of IL-1 beta, TNF-alpha, IL-6, and soluble C5b-9 (SC5b-9) was examined for 23 patients with iMGN, 16 patients with diabetic nephropathy (DNP), and 17 healthy subjects. IL-1 beta excretion (pg/mg crea) was significantly higher in iMGN patients (375, range 162-11,000) than in DNP patients (39, range 22-59, P < 0.001) or healthy controls (151, range 23-481, P < 0.001). TNF-alpha excretion rate (pg/mg crea) was clearly higher (38, range 21-700) in iMGN patients than in DNP patients (14, range 8-52, P < 0.001) or healthy subjects (11, range 7-26, P < 0.001). Median IL-6 excretion (pg/mg crea) was only marginally higher in iMGN patients (73, range 0-850) than in healthy subjects (64, range 3-158, P = 0.02) but significantly higher than in DNP patients (29, range 17-47, P < 0.001). No significant correlation with corresponding serum values was observed for urinary IL-6 or TNF-alpha excretion. Urinary IL-1 beta and TNF-alpha correlated with decreased renal function. Five of 23 patients showed progression of iMGN over a follow-up of 6 months. The excretion of all cytokines, TNF-alpha in particular, was significantly higher in patients with a progressive disease than in the other patients.(ABSTRACT TRUNCATED AT 250 WORDS)