On the basis of their response to corticosteroid therapy, 22 nephrotic children who have demonstrated continuous or recurrent disease activity for five or more years, and one other child who died in recent years of uremia after a protracted course, are divided into three clinical groups defined as follows: (1) corticosteroid sensitive, (2) corticosteroid dependent, (3) corticosteroid resistant. On light microscopy study, minimal or no pathological change was noted in all ten patients of group 1. Of six children in group 2, three had minimal disease or no pathologic findings; the others varied from mild to moderate and the disease was usually sclerotic in type. Significant pathologic conditions were noted in five of six patients in group 3, ranging from proliferation to glomerulosclerosis. Progression from minimal change to membranoproliferative disease to sclerotic disease was noted in one patient. Clinical response to corticosteroid therapy is a reliable indicator of current pathologic status.