Three children with renal disease, hypertension, and the Cockayne syndrome were evaluated. All patients had severe hypertension; peripheral vein renin was elevated in two patients. Renal biopsy specimens from two patients were studied by light microscopy, electron microscopy, and immunofluoresence. Immunohistologic studies demonstrated deposits of immunoglobulin and complement in the vessels and glomeruli of the first patient; deposits of immunoglobulin and complement were seen in the glomeruli of the third patient. Also electron-dense deposits were seen in the glomerular basement membrane of the third patient. Circulating immune complexes were detected by the Raji cell and Clq binding techniques in this child as well. Both hypertension and renal disease are frequent complications of the Cockayne syndrome.