Since 1992 we have treated 11 children with frequently relapsing steroid-sensitive (n=6) or steroid-resistant (n=5) nephrotic syndrome with levamisole. All had been non-responsive to other immunosuppressive medication before levamisole treatment. All steroid-sensitive patients had signs of steroid toxicity. At least 1 kidney biopsy had been performed prior to study in each patient. Five children had minimal glomerular changes and the other 6 focal segmental glomerular sclerosis. The patients were treated with levamisole (2.5 mg/kg per 48 h) for at least 2 months (up to 18 months, median 10 months). Two patients had additional immunosuppression (cyclosporine A) during levamisole treatment. All patients with steroid-sensitive nephrotic syndrome became free of proteinuria within 2 months and have remained in remission after discontinuation of levamisole (follow-up time 8-50 months, median 24 months). None of the children with steroid-resistant nephrotic syndrome experienced a remission. Side effects were observed in 2 patients and included a granulocytopenia and a severe psoriasis-like cutaneous reaction; both were reversible after discontinuation of levamisole. We conclude that levamisole is of benefit in steroid-sensitive nephrotic syndrome but not in steroid-resistant nephrotic syndrome.