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Cardiac autonomic neuropathy is a frequent complication of diabetes leading to resting tachycardia, postural hypotension, painless myocardial ischaemia, rhythm disturbances and sudden cardiac death. The aim of the study was to evaluate in a diabetic population the sensitivity of two exploration modes of autonomic neuropathy in diabetics: the Ewing tests which are, at present time, the reference method and the (123-I) meta-iodo-benzyl-guanidine (MIBG) single photon emission computed tomography (SPECT) which evaluates the cardiac sympathetic innervation.9 male insulin-dependent diabetes mellitus patients were studied. Mean age was 40.7 +/- 15 years and diabetes duration was 10.8 +/- 6 years. None had hypertension or macroangiography as demonstrated by patient's history, clinical examination, rest and exercise electrocardiography and ambulatory blood pressure monitoring. The complications observed were background retinopathy in 2 patients, incipient nephropathy in 3 and a peripheral neuropathy in 1 patient. Ewing tests, i.e. Valsalva maneuver, beat to beat heart rate variation during deep breathing and standing, blood pressure response to standing and to sustained handgrip, were performed. The results were considered as pathologic when the score was over 2. After injection of 10 mCi (123-I) MIBG, planar images were realized at times 1, 2 and 4 hours and SPECT images after 2 hours. The heart/mediastinum uptake ratio was calculated.We noted abnormalities of planar images in 3 patients, SPECT images in 1, and both in 1 patient. None was positive for Ewing tests.Although MIBG SPECT will explore only the sympathetic innervation, these preliminary findings suggest that this technique could be more sensitive for the evaluation of cardiac autonomic neuropathy. Nevertheless cost and lack of disponibility of this technique should limit its use.