The nephropathology associated with retroperitoneal fibrosis has been commonly related to compression of the ureters and hydronephrosis. This assumption has been made without the use of immunofluorescent microscopy and electron microscopy. The authors studied renal tissue from a patient with retroperitoneal fibrosis by light microscopy, immunofluorescent microscopy and electron microscopy. In addition to the gross and microscopic changes of obstructive nephropathy, histologic findings of glomerular immune-complex deposition were also present. It is postulated that in some cases of retroperitoneal fibrosis, destruction may be mediated by both obstructive and immunologic processes.