In this study, we report quantity, solubility and molecular polymorphism of collagen, proportional relationships between various types of collagen, ultrastructure of collagen fibres, the amounts of various glycosaminoglycans (GAGs) and proportional relationships between them in Wharton's jelly of normal umbilical cords. We compare the extracellular matrix components in Wharton's jelly with those in the umbilical cord artery. Collagen of the Wharton's jelly demonstrates some specific features. It is very insoluble in neutral salt and in a slightly acidic solution and appears to be resistant to the action of depolymerizing agent (EDTA-Na2). Only 50% of total collagen may be solubilized by pepsin digestion and fractionated by differential salt precipitation. Four collagen fractions were obtained. Three of them were identified by polyacrylamide gel electrophoresis as type I, type III, and type V collagen and proportional relationship between them was calculated. Hyaluronic acid is the most abundant component of GAGs contained in Wharton's jelly. The amounts of sulphated GAGs-keratan sulphate, heparan sulphate, chondroitin-4-sulphate, chondroitin-6-sulphate, dermatan sulphate and heparin-are distinctly lower. Each of them constitutes only a few percent of total GAGs.