Gestational diabetes mellitus (GDM) identifies a population of women at high risk of subsequent type 2 diabetes mellitus, representing an early stage in the natural history of the disease. Systemic inflammation is associated with the development of type 2 diabetes but the data concerning pro- and anti-inflammatory cytokines in patients with GDM are limited. The aim of our study was to investigate serum concentrations of interleukin-8 (IL-8), IL-18 and IL-10 in pregnant women with various degree of glucose intolerance. The group studied consisted of 58 patients with GDM, 31 pregnant women with normal glucose tolerance (NGT) and 32 women with an abnormal result of a 50 g glucose challenge test (GCT) but a normal result of 75 g oral glucose tolerance test (OGTT). Serum IL-8, IL-10, IL-18 and CRP concentrations were measured by immunoenzymatic assays. Patients with GDM had markedly higher IL-8 and IL-18 levels than women with NGT (3.86±5.44 vs 0.8±0.57 pg/ml, P=0.00001 and 264.4±111.98 vs 203.57±108.14 pg/ml, P=0.0005, respectively), as well as significantly lower IL-10 concentrations (1.37±2.04 vs 2.86±1.53 pg/ml, P=0.00001). There were no significant differences in interleukin levels between patients with NGT and abnormal GCT. There were significant correlations between IL-8 concentration and prepregnancy BMI (R=0.2093, P=0.031), insulin (R=0.42075, P=0.00004), HOMA-IR (R=0.45857, P=0.000001), and glucose (R=0.2030, P=0.03), as well as between IL-18 level and insulin (R=0.20055, P=0.0301) and HOMA-IR (R=0.20385, P=0.028). IL-10 correlated inversely with insulin (R=−0.26822, P=0.0036) and HOMA-IR (R=−0.29127 P=0.0016). CRP correlated with insulin (R=0.28875 P=0.0017) and HOMA-IR (R=0.28836, P=0.0019). Our results suggest that GDM is associated with elevated concentrations of pro-inflammatory cytokines IL-8 and IL-18, as well as with low level of anti-inflammatory IL-10. This association seems to be mediated in part by the indices of insulin resistance.