It has previously been considered inevitable that a progressive deterioration in renal function would occur in type I diabetics who have proteinuria in the nephrotic range. We have reviewed all type I diabetic patients presenting with nephrotic-range albuminuria to this department over a 13-year period. Of 16 patients identified, 4 have demonstrated a prolonged stability of renal function, with 2 losing their albuminuria. The latter 2 patients, who have been treated with an angiotensin-converting enzyme inhibitor for over 11 years, are presented in detail. The possible factors contributing to progression and the role of angiotensin-converting enzyme inhibitors in the treatment of advanced diabetic nephropathy are discussed.