We have investigated the possibility of application of the direct mass-spectrometric analysis of plasma metabolites for diagnostics of impaired glucose tolerance (IGT). The plasma samples obtained from the control group of patients showing no disturbances of carbohydrate metabolism (n=30) and those with IGT (n=20) were treated with methanol to precipitate proteins and the residual fractions were analysed on a quadrupole flight-of-time mass-spectrometer. A total of 230 metabolites were identified the levels of which were attributable to IGT. The accuracy of diagnostics using the mass-spectrometric analysis was 92% (specificity 94%, sensitivity 89%, area under the Roc-curve 0.94, reproducibility 85%). The detected metabolites included endocanabioids, cresol, ornithine, phospholipids, and fatty acids the presence of which was related to the previously described risk factors of diabetes mellitus. It is concluded that the direct spectrometric analysis of plasma metabolites can be used in routine clinical practice as a more rapid and better reproducible alternative method in comparison with the glucose tolerance test .