The aim of the present preliminary study was to describe a simple protocol for the analysis of the heart rate variability (HRV) that can reveal the different autonomic control between noncomplicated diabetic patients and normal subjects within 15 min. The power spectrum of the HRV was evaluated on 5-min-long electrocardiographic recordings in both the supine and the seated positions in 30 noncomplicated non-insulin-dependent diabetic (NIDDM) patients and in 30 healthy volunteers. In healthy subjects the low-frequency (LF) value was higher in seated position than in supine position, while in diabetic patients the LF value in seated position did not differ from that in supine position and did not differ from that in healthy subjects in supine position. The present work demonstrates that the protocol described reveals a different autonomic regulation of the heart rate in healthy subjects and in NIDDM patients even if there is no clinically evident autonomic neuropathy.