The occurrence of idiopathic nephrotic syndrome may be due to environmental antigens, and in particular to the ingestion of certain foods, as indicated by the result of food eviction tests. This led us to prescribe oral cromoglycate (800 mg/day for 2 weeks) combined with the avoidance of specific foods. Twelve patients with corticosteroid-dependent (n = 6) or corticosteroid-resistant (n = 6) idiopathic nephrotic syndrome with proteinuria greater than 1.50 g/24 h were thus treated without modification of steroid dosage. In 3 of these patients hypersensitivity to certain foods had previously been demonstrated. In 5 of the 12 patients, proteinuria was reduced by more than 50 percent; these 5 patients had received cromoglycate for 2 weeks with a free diet. After evictions were stopped, 3 patients relapsed; in 2 cases proteinuria remained absent. In 3 of the 12 cases, we subsequently used cromoglycate and evictions in corticosteroid-dependent patients in complete remission by gradual reduction of steroid dosage in the hope of lowering the dependence threshold. In one patient, the corticosteroid therapy could be discontinued during 3 months without relapse; in the other 2 patients no effect was observed. Thus, oral cromoglycate could be used together with food eviction in certain cases of idiopathic nephrotic syndrome, this being a therapeutic approach as well as a diagnostic test.