BACKGROUND: Urinary levels of cytokines may function as indices of renal disease activity. METHODS: This study was designed to investigate the urinary excretion of IL-6 and TGF-beta in the patients with IgA nephropathy(IgAN) and the effects of AII receptor blockers(ARB : losartan) on it. RESULTS: The patients with IgAN(n=10) showed higher urinary excretion of IL-6 and TGF-beta than normal controls(n=7). There is a positive correlation between IL-6 and TGF-beta. Urinary excretion of IL- 6 was positively correlated with proteinuria in IgAN (IL-6 : gamma2=0.560; p < 0.05) but not with serum creatinine. After 2 months of ARB therapy in IgAN patients, urinary excretion of IL-6 was decreased(IL-6 : 11.3+/-7.7 vs 5.3+/-3.3 pg/mg Cr, p < 0.05). Positive correlations were noticed in ARB group between urinary cytokines and proteinuria. CONCLUSION: Our data suggest that the patients with IgAN showed higher urinary excretion of IL-6 and TGF-beta. and the IL-6 excretion can be effectively reduced by ARB therapy.