Diabetes mellitus and surgical ablation of renal tissue are two independent influences associated with hyperfiltration and elevated levels of the glomerular transcapillary hydraulic pressure differential (delta P). There is increasing evidence that hyperfiltration with elevated delta P is pathogenic and leads to glomerular damage. The authors questioned whether these two influences (surgical ablation of renal tissue and diabetes mellitus) would act in an additive fashion in human patients to produce an accelerated decline in renal function. Three patients with non-insulin-dependent diabetes mellitus who had undergone a unilateral nephrectomy (for a variety of reasons) were (retrospectively) identified. In each patient, morphologic evidence of diabetic glomerulonephropathy was present in the resected kidney. The charts from these patients were reviewed and post-nephrectomy renal function was estimated over time by plotting reciprocal serum creatine values versus time. Follow-up intervals after nephrectomy varied from 4 to 15 years. The results of our follow-up showed no obvious detrimental effect on renal function (as measured by 1/serum creatinine) attributable to the unilateral nephrectomy. The authors conclude that residual renal function (and ultimate outcome) in patients with non-insulin-dependent diabetes mellitus is highly variable, but does not seem to be adversely affected (at least over the time span of observation in these patients) by unilateral nephrectomy.