A retrospective study was performed in 68 patients diagnosed as having idiopathic nephrotic syndrome with steroid-dependent, steroid-resistant or frequent relapse subtypes at the Department of Pediatrics, Siriraj Hospital during Jan 1996-Dec 2004. Male to female ratio was 3.3:1 and mean age (+/- SD) was 8.4 +/- 3.5 years. Mean follow up time (+/- SD) was 47.4 +/- 30.5 months. Renal biopsy was done in 60 patients, showing IgM nephropathy in 73.3%. Fifty-four patients (79.4%) received cyclophosphamide at a dose (+/- SD) of 2.2 +/- 0.5 mg/kg/d for 11.6 +/- 3.4 weeks. Negative proteinuria at 1 year was found in 70% and prednisolone was discontinued in 52%. Leucopenia was found in 9.2%. At last follow up, 34% of the patients were still in remission. Enalapril was prescribed in 50 patients for 12.4 +/- 10.0 months. Thirty-six patients also received cyclophosphamide. Remission at 1 year was achieved in 66% and prednisolone discontinued in 28%. Twelve patients (24%) were still in remission at last follow up. The results of 3 regimens: cyclophosphamide, enalapril, and cyclophosphamide plus enalapril were compared using chi-square test. Remission was significantly better in cyclophosphamide group (p = 0.014). Dipyridamole was prescribed in 14 patients due to thrombocytosis. Only 2 of 14 patients achieved remission although 11 patients received cyclophosphamide plus enalapril, and another 2 patients received only cyclophosphamide. Complications included hypertension (44%), cataract (40%), glaucoma (15%), short stature (17.6%), and obesity (5.9%). Recurrent infection was found in 69%, including dental caries (16.29%), urinary tract infection (14.7%), intestinal parasitic infestration (10.3%), respiratory tract infection (8.8%), and skin infection (7.4%). Chronic renal failure was found in 3 patients and portal vein thrombosis was found in 1 patient. We suggest that cyclophosphamide should be used as first line drug in difficult-to-treat nephrotic syndrome patients. Enalapril may be beneficial in some patients. Thrombocytosis may be associated with poor response to both medications. Difficult-to-treat patients also need long-term follow up and surveillance for complications due to disease and/or treatment.