Objective: To investigate the clinical and pathological features of idiopathic membranous nephropathy (IMN) in Chinese adults. Methods: From 1986 to 1997, 264 patients with biopsy proven membranous nephropathy were selected in this study. Clinical and pathological features were compared between patients at different ages by t test. Results: (1) Patients from 21- 40 years old were inclined to membranous nephropathy. (2) One hundred and six of the patients had heavy proteinuria at presentation. Hypertension was found in 35 patients. Renal insuffeiency occurred in 7.7% of the patients in renal biopsy. Microscopic hematuria was found in 40.2% of the patients. Seventy-four patients presented nephrotic syndrome. (3) Eight of the 57 patients had deterioration of renal function during an average 49-month follow-up. (4) Patients of stage Ⅰ, Ⅱ, Ⅲ and Ⅳ accounted for 42.3%, 48.7%, 6.0% and 3.0% respectively. Glomeruli IgG, C3 and C1qdeposition was found in 93.2%, 98.8% and 58.3% of the patients. Conclusion: Younger patients are inclined to membranous nephropathy. The incidence of hypertension, microscopic hematuria and renal insuffcieney is similar to that of other countries, while nephrotic syndrome is uncommon.