We measured the urinary levels of active transforming growth factor-beta (TGF-beta) by enzyme-linked immunosorbent assay in 12 healthy controls and 42 patients with various glomerular diseases, including mesangial proliferative (IgA nephritis, Henoch-Schönlein purpura nephritis, and IgA-negative mesangial proliferative glomerulonephritis) and non-proliferative (minimal change nephrotic syndrome and focal glomerulosclerosis) types. Urinary TGF-beta, expressed as a ratio to urinary creatinine (ng/mg creatinine), was elevated in patients with IgA nephritis and focal glomerulosclerosis, and was significantly higher than in patients with other types of glomerular diseases and healthy controls. There was a significant correlation between urinary TGF-beta levels and the grade of interstitial fibrosis. Among patients with proliferative-type disease, urinary TGF-beta was significantly correlated with the grade of mesangial matrix increase and the magnitude of proteinuria. The relationship between urinary TGF-beta levels and the immunostaining intensity of TGF-beta in the glomeruli was not significant. These results indicated that urinary TGF-beta reflects the grade of interstitial fibrosis in glomerular diseases and also the mesangial matrix increase in proliferative-type glomerulonephritis. Measuring TGF-beta levels in the urine might be helpful in monitoring patients with some types of glomerular disease.