We retrospectively studied the clinical course and treatment outcome of idiopathic membranous nephropathy (IMN) amongst 38 Chinese patients (25 male, 13 female, age 51.6 +/- 14.6 years, follow-up duration 58.2 +/- 51.1 months) who presented over a 10-year review period. Eight never received any form of specific treatment (group I), seven received oral corticosteroid alone for 6-9 months (group II), 17 were given corticosteroid plus cyclophosphamide for 6-12 months (group III), and six were treated with methylprednisolone alternating with chlorambucil every other month for 6 months (group IV). No untoward effect from drugs sufficient to alter the dosage used was recorded. After 6 months of treatment, over 50% of patients went into remission: a significant reduction in proteinuria (p = 0.01, 0.01, 0.02) with a corresponding rise in serum albumin levels (p = 0.01, 0.01, 0.04) was observed in groups II, III, and IV, respectively, but not in group I. During follow-up, one patient in each of groups I, III, IV, and two of group II developed renal function deterioration, which correlated with an abnormal presenting serum creatinine. In six group I and eight group III patients who have been followed for at least 5 years, there was progressive reduction in proteinuria in group III (p < 0.05), but not in group I: serum creatinine has remained unchanged in both groups. IMN runs a benign course in Chinese patients in Hong Kong, with 2.6% of patients going into end-stage renal failure during the study period. Contrary to reports in Caucasians, there is similar treatment response to steroid alone or a combination of steroid and cytotoxic agents.