Klinefelter syndrome is a hypergonadotropic hypogonadism determined by the presence of one or more extra X chromosomes and has an incidence of 1:800 males. It was shown that in Klinefelter syndrome mortality is increased due to diabetes, cardiovascular, respiratory and digestive diseases. Our goal was to assess the presence of metabolic changes which can increase cardiovascular risk. We compared 31 untreated Klinefelter patients aged 19-54 years (mean age 33.84 years, SD 11.79 years) with 31 age matched controls. Hypercholesterolemia was present in 56.67% of Klinefelter patients and correlated with age and the magnitude of androgenic deficit. None of the patients had diabetes mellitus but glycemic values above 100 mg% were present in 16.13% of cases (vs 3.2% in controls). 35.5% of Klinefelter patients and controls were overweight and 16.1% of Klinefelter patients were obese vs 9.7% of controls.