33 subjects belonging to I.G.T. class according to N.D.D.G. criteria and controlled in our ambulatory, have been studied for the response to the tests usually employed for the investigation of parasympathetic and sympathetic cardiovascular innervation. We have found pathological values for the SL1 test and borderline values for SL2 and LS tests; on the contrary all the other tests presented normal values. The Authors conclude that signs of deterioration of cardiac and vascular innervation, especially regarding the parasympathetic nervous system, can be present also in the subjects showing a small glucose metabolism alteration. This subclinical alterations do not depend on factors which can interfere with the responses to the tests (as age, boyd weight, sex and presence or absence of diabetic familiarity) but on glucose metabolism alteration. Hence also the subjects with I.G.T. have to be considered as a at risk population, like the neuropathic diabetics.