Objective: to study structural changes in the germinal matrix (GM) in 22-to-40-week fetuses with ventriculomegaly (VM) and hydrocephalus (HC). Material and methods. The width of the ventricular groove was borne in mind while forming study groups (the brain in VM (n=30), HC (n=20)) and a comparison group (n=30). To trace changes in GM transformation, each group was divided into 4 subgroups according to the gestational sign. Materials were excised in the projection of the lateral ventricles onto the convexital surface of the brain. After the use of conventional methods, the specimens were stained with hematoxylin and eosin or Nissl. Results. VM was found to be characterized by the early (at 22 weeks' gestation) regionalization of glio- and neuroblasts and by the completion of GM reduction at 35 weeks of intrauterine development. In HC, GM in all ventricular system regions was preserved and its structure was virtually unchanged at 22 to 40 weeks' gestation. Conclusion. The found structural changes may be used as diagnostic criteria for VM and HC and to elucidate gestational age in forensic medical practice.