Abstract Objectives: To find out if determination of IL-4, IL-13 and IL-6 in amniotic fluid (AF) and serum in mid-pregnancy can be used as predictors of preterm delivery. Material and methods: The research has comprised 88 pregnant women at 16-24 weeks of gestation, who were subjected to early amniocentesis. Levels of interleukins were determined by ELISA tests. Pregnant women had been monitored untill termination of pregnancy and divided in two groups: 68 term and 20 preterm deliveries. Results: IL-13 was not detectable at all in serum and amniotic fluid samples. IL-4 was not detectable in serum samples of both groups of women and it was detectable only in small number (20 % - 27 %) of AF samples. There was no statistically significant difference (p=0.665) in the mean values of AF IL-4 levels between the examined groups of women. Detectability for IL-6 was very low in serum specimens, while in AF it was detectable in 100% of cases and its levels was significantly higher (p<0.001) in preterm delivery group. Conclusions: The results obtained in this study suggest that the AF mid-pregnancy levels of IL-6 higher than 132 pg/ml may indicate preterm delivery.