A prospective study was performed to evaluate the efficacy of chlorambucil in inducing long-term remission in children with steroid-dependent or cyclophosphamide-resistant primary nephrotic syndrome (NS). The 15 steroid-dependent children had a relapse rate of 5.3/patient per year (range 4–8) and a mean age of 8.4 years (range 2–13). The chlorambucil dosage was 0.2 mg/kg per day for a total of 8 weeks. Nine patients (56%) remained in complete remission for an average of 39.2 months (range 16–70). The interval to the first relapse in the remaining 7 ranged from 4 to 41 months and the relapse rate decreased significantly to 0.6 relapses/patient per year (P<0.05). five="" children="" had="" steroid-="" and="" cyclophosphamide-resistant="" ns,="" 4="" with="" focal="" segmental="" glomerulosclerosis="" and="" 1="" with="" mesangiol="" proliferative="" glomerulonephritis.="" chlorambucil="" was="" given="" in="" a="" dose="" of="" 0.2="" mg/kg="" per="" day="" for="" 8–16="" weeks.="" complete="" remission="" was="" obtained="" in="" 4="" patients;="" 2="" patients="" relapsed.="" no="" serious="" long-term="" complications="" were="" observed="" in="" our="">