Very little is known about the presence of autonomic neuropathy in subjects with slight abnormalities of glucose metabolism. This study was carried out to investigate whether impaired glucose tolerance (IGT) is associated with abnormalities of beat-to-beat variation (BTBV). Sixty-two subjects, aged 40-59 years, with IGT (according to EASD criteria) and 124 normals, matched for age, sex and body mass index (BMI), were selected among the participants in a health examination survey and tested for BTBV. Among the possible factors influencing this test, sex did not shown any effect, while age and BMI were significantly and negatively correlated to BTBV in both groups. Glucose intolerance was not associated with any impairment of BTBV which was almost identical in the normal (15.8 +/- 6.3 beats/min) (mean +/- SD) and in the IGT group (16.7 +/- 7.0 beats/min). Similarly no significant difference was found in BTBV between subjects with constant IGT or normal results at OGTT, repeated on two occasions. All subjects were then stratified according to blood glucose values 2 h after an oral glucose load (after load): only those with blood glucose after load greater than 200 mg/dl displayed a significant decrease in BTBV (9.7 +/- 3.8 beats/min) compared to those found normal at the glucose tolerance test (p less than 0.025). They were also the only ones with an average HBa1 level significantly higher than in normal individuals (p less than 0.005). In conclusion, IGT is not associated with abnormalities of BTBV.