Adiponectin and tumor necrosis factor-alpha (TNF-alpha) have been implicated in insulin resistance and diabetes mellitus (DM). In the present study we investigated levels of adiponectin and TNF-alpha and their relationships with each other and metabolic factors in women with gestational DM (GDM). Thirty-four pregnant women with GDM and 31 pregnant women with normal glucose tolerance (NGT) were included in the study. Plasma adiponectin levels were lower in GDM than in NGT (36.9 +/- 6.7 vs. 61.3 +/- 13.0 ng/ml, p = 0.028). Serum TNF-alpha levels were increased in GDM compared with NGT (20.5 +/- 2.4 vs. 14.0 +/- 1.5 pg/ml, p = 0.042). After adjustment for pre-pregnancy and current body mass index (BMI), adiponectin levels correlated negatively with insulin resistance by homeostasis model assessment-insulin resistance (HOMA-IR) and 0-h and 1-h glucose both at glucose challenge test and oral glucose tolerance test in GDM. Adiponectin levels were correlated only with very low-density lipoprotein cholesterol and triglyceride levels in NGT. TNF-alpha levels were correlated with glycated hemoglobin in GDM. There was a significant positive correlation between TNF-alpha levels and pre-pregnancy and current BMI in GDM as well as NGT. HOMA-IR for adiponectin and pre-pregnancy BMI for TNF-alpha remained as significant determinants in multiple regression analyses. In conclusion, these data suggest that reduced adiponectin and increased TNF-alpha may be involved in the pathogenesis of GDM.