Concentrations of glucose, bilirubin, H+ ions, estriol, HPL were determined in the samples of amniotic fluid from post term and near term pregnancies. Investigated group consisted of samples taken between 42-43 week of gestation, control group between 38-40 week. In both groups biochemical tests of pulmonary maturation--Lectin/Sphingomyelin ratio, foam test, 650 nm absorbance were carried out. In the diagnosis of post term pregnancy glucose concentrations, oestrogens, HPL, 650 nm adsorption, foam test and L/S ratio had proper diagnostic value. No differences were observed in bilirubin concentrations.