Sixty-six patients of all ages whose renal biopsy appearances satisfied strict criteria for the histopathological diagnosis of membranous nephropathy were studied and followed for a mean of 5-4 years (range 1 to 20 years). From initial investigation seven patients were found to have associated neoplasia, and in two patients the condition followed treatment with a mercurial diuretic and gold. One patient was Australia antigen positive. Two patients developed renal vein thrombosis, but in both this appeared to follow not precede their nephrotic syndrome. In the remaining 56 patients there was no associated factor.

During the follow-up period, approximately one-quarter of the patients (15) died, nine from renal failure; one-quarter (10) had a persistent nephrotic syndrome, another one-quarter (15) proteinuria of lesser degree. The final one-quarter (16) are now in complete remission. The prognosis of the 54 patients with an initial nephrotic syndrome was poorer than the 12 with lesser proteinuria and no oedema at onset; five of 11 children were in complete remission when last seen. All but one of the nine patients who developed terminal chronic renal failure 4 to 18 years from onset had an unremitting nephrotic syndrome, and eight of the 10 currently alive with a persistent nephrotic syndrome have reduced renal function. Renal functional deterioration did not occur in the absence of proteinuria.

There was only slight correspondence between the stage of biopsy appearance, glomerular filtration rate at time of biopsy, time of the biopsy from apparent onset, or status at last follow-up. Staging is therefore of limited prognostic value. Twenty-two patients were treated with corticosteroids for 2 to 36 months; we detected no short or long-term benefit when compared to patients not so treated.