Proteoglycans – high molecular polysaccharide-protein-complex compounds – are very important in vital intracellular and extracellular metabolic functions. Disturbances of their regulatory mechanisms are followed by an increase of their rate of biosynthesis. This obviously causes a partially irreversible damage in the connective tissue of the skin which is clinically and morphologically visible, especially in the so-called collagen diseases. Examination of the metabolism of the mucopolysaccharides of the skin is made possible by the quantitative estimation of the mucopolysaccharides in the urine. An increased elimination of the proteoglycans is discussed as well as the value of the met