We studied kidney biopsy specimens from three children with sickle cell anemia and microangiopathic glomerulopathy. One child also had cyanotic congenital heart disease. Laboratory evaluation revealed proteinuria and normal serum creatinine in all and normal serum complement in two of the three children at the time of biopsy. In all biopsies, glomeruli were enlarged with diffuse hypercellularity and focal segmental mesangial interposition; capillary loop lumens were congested with sickled erythrocytes. Immune labeling identified segmental immunoglobulin G, C3, and properdin over the glomerular capillary loop walls in each case. Ultrastructurally, the subendothelial zone of the glomerular basement membrane was widened with new lamina densa formation with focal mesangial interposition. The glomerular lesion we describe in these children may be due to endothelial injury related to the altered erythrocytes, glomerular hemodynamics, and the hypercoagulable state characteristic of sickle cell disease.