We aimed to evaluate plasma asymmetric dimethylarginine (ADMA) concentrations and its relation with insulin sensitivity/resistance indices in pregnant women with different degrees of carbohydrate intolerance. This study included a two step approach; 50 g glucose challenge test (GCT) followed by 100 g oral glucose tolerance test (OGTT) was used for diagnosis of carbohydrate intolerance within 24-28th weeks of gestation. Pregnant women with positive GCT but negative OGTT (AGCT group, n = 30) and gestational diabetics (GDM group, n = 58) were compared to healthy pregnant controls (n = 50). Plasma ADMA concentration and its relationship with glucose and insulin levels and insulin sensitivity/resistance indices (HOMA-IR, QUICKI, ISIOGTT) were evaluated. Both AGCT and GDM groups were found to have similarly higher plasma ADMA levels than control subjects (3.60 +/- 1.21; 4.00 +/- 1.70; 2.65 +/- 0.82 mu mol/l, respectively, P = 0.001). ADMA was significantly but slightly correlated with insulin sensitivity/resistance indices and moderately correlated with 2-h insulin level. The 2-h insulin value of the OGTT was the independent influencing constant for ADMA (R = 0.57, P = 0.0001). In conclusion, plasma asymmetric dimethylarginine level was higher in cases with abnormal glucose challenge test but normal OGTT as well as in gestational diabetics, compared to pregnant women with normal glucose tolerance. The elevated ADMA level in pregnant women with carbohydrate intolerance may possibly be due to elevated insulin level.