The purpose of this review is to enhance the clinical awareness of the association between membranous glomerulonephritis and neoplasia. Controversy has persisted that has tended to minimize this association, therefore, we report our experience to shed some light on this controversy as well as to make diagnostic recommendations. One hundred seven adult patients with biopsy-proven membranous glomerulonephritis were selected for review. Twenty of these patients had a known secondary cause of membranous glomerulonephritis other than malignancy. Data were collected retrospectively on all these patients and nine were found who had or developed malignancy associated with membranous glomerulonephritis. Clinical data were analyzed to ascertain the onset of renal disease in relation to the malignancy as well as to determine the ultimate patient and renal outcome after treatment of the neoplasm. Of the 87 patients with presumed idiopathic membranous glomerulonephritis, nine (10.3%) had or developed a malignancy associated with their renal disease. The membranous glomerulonephritis was seen in patients with various solid tumors as well as hematologic malignancies. All patients presented with nephrotic-range proteinuria. Proteinuria manifested itself prior to or concomitantly with the diagnosis of the neoplasm in approximately 80% of cases. Follow-up data were available on seven patients: complete remission of proteinuria was seen in two patients associated with treatment of their tumors, one patient developed end-stage renal disease, and the remaining four patients had persistent proteinuria associated with tumor recurrence or metastasis. There appears to be a clear association between membranous glomerulonephritis and neoplasia.(ABSTRACT TRUNCATED AT 250 WORDS)