We investigated the relation between diabetic autonomic neuropathy (DAN) and left ventricular (LV) function in 59 patients with type 2 diabetes mellitus (T2DM) free of coronary artery disease (CAD) or hypertension. Diabetic autonomic neuropathy was established by ≥2 abnormal autonomic nervous function tests. Left ventricular systolic and diastolic functions were assessed by resting radionuclide ventriculography. Compared with non-DAN patients (n = 24), patients with DAN (n = 35) had an increased adjusted atrial contribution to ventricular filling (A/V%, 30.1% ± 8.2% vs 26.5% ± 5.1%; P = .031), suggestive of diastolic dysfunction (DD). There were no differences between the 2 groups in peak filling rate, first 1/3 filling fraction, ejection fraction, cardiac output, and cardiac index. Patients with diabetic autonomic neuropathy had an increased heart rate (77.8 ± 6.3 vs 69.3 ± 3.3 bpm; P < .0001) and a higher rest LV workload (10 072 ± 1165 vs 8606 ± 1075 bpm mm Hg; P < .0001). Patients with DAN T2DM without CAD or hypertension have DD, increased A/V index, and a higher LV working load than non-DAN patients.