Serum interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF alpha) concentrations were measured in subjects during two-hour glucose loading in order to investigate the effects of glucose on serum IL-6 and TNFa concentrations. Twenty-six female subjects (mean age 60 10 years) had normal glucose tolerance (NGT) and nineteen female subjects (mean age: 63 9 years) had impaired glucose tolerance (IGT) according to WHO criteria. Serum IL-6 and TNF alpha concentrations were measured by chemiluminescent immunometric assay. Subjects with IGT have higher fasting serum TNF alpha levels than subjects with NGT (p < 0.01). Serum IL-6 and TNFa concentrations were elevated during glucose loading (for each comparision, p < 0.01). The increase in serum TNF alpha concentrations in IGT was greater than in NGT (p < 0.01). Serum IL-6 and TNF alpha concentration significantly correlated with insulin and glucose in IGT group (for each comparision, p < 0.01). The correlation between serum glucose and cytokines concentrations was significant in IGT (for each comparision, p < 0.01). There was also a positive correlation between serum IL-6 and TNFa in NGT and IGT (for each comparision, p < 0.01). In conclusion, hyperglycemia is associated with increased circulating cytokine concentrations and fasting TNF alpha concentrations seem to be more associated with IGT than IL-6.