Introduction. Up to date studies dealing with embryogenesis of the pulmonary trunk and arteries seldom analyze the anatomical variations between sexes and proportions of the pulmonary arteries dimensions. A large number of investigated subjects in our study enabled a detailed description of the growth of the pulmonary trunk and pulmonary arteries. Other studies involved fewer subjects. Aim. We aimed at investigating the development of the pulmonary trunk and its branches, i.e., the left and the right pulmonary arteries, during a period between the 4th and 8th months of fetal life. Materials and methods. We investigated 223 human fetuses, including 108 males and 115 females, aged between 4 and 8 months of prenatal life. All fetuses had been conserved for a minimum period of 3 months in a 9% formaldehyde solution. All fetuses of a normal karyotype were obtained from spontaneous abortions and none of them revealed any external signs of malformations. We measured the diameters of the initial part of the pulmonary trunk and of the two main arteries: right and left pulmonary arteries. We determined the mean value of each assessed parameter for every age group, the rate of growth of particular vessels, the variations in these parameters with relation to sex, and the ratio between the left and the right pulmonary artery dimensions. For statistical analysis ANOVA, regression analysis, and Tukey’s HSD post hoc test were used. Results, Discussion and Conclusions. The growth of the diameters of pulmonary vessels (pulmonary trunk, left and right pulmonary arteries) is linear in time. The vessel dimensions do not differ with regard to sex. Only in the 5th month was the pulmonary trunk statistically significantly wider in female fetuses. The left pulmonary artery is smaller than the right one.