Hypertension is highly prevalent in type 2 diabetic patients (NIDDM) with nephropathy, and is the single most important determinant of the rate of renal function loss. In many of these patients, hypertension is resistant to therapy. Although increased sympathetic activity is also highly prevalent in NIDDM patients with nephropathy and chronic renal insufficiency, little attention has been paid to sleep apnea as the cause of both resistant hypertension and sympathetic hyperactivity in this population. Since the prevalence of sleep apnea is increased in patients with either NIDDM, or resistant hypertension, or chronic renal insufficiency, it is almost certain that sleep apnea has a high prevalence in patients in whom all three states co-exist, i.e. NIDDM patients with nephropathy and hypertension resistant to therapy. As a consequence of undetected and untreated sleep apnea, resistant hypertension, nocturnal hypertension, and sympathetic hyperactivity likely contribute to accelerated loss of renal function and increased cardiovascular morbidity and mortality in these patients.