Urine samples of five patients with epidermolysis bullosa hereditaria were examined for the presence of acid glycosaminoglycans (GAG) and compared to 10 healthy subjects. A significant increase (p less than 0.0005) could be detected in patients with epidermolysis (t = 6.66, means: 49.7 mg/day, standard deviation: +/- 18.3). Additionally, acid glycosaminoglycan concentration in sweat of patients and healthy controls was determined but statistical calculations showed no significant difference (p less than 0.15). On grounds of the increased mucopolysaccharide excretion and the previous studies of collagen-glycosaminoglycan interactions, we strongly suggest that acid GAG are involved in the pathogenesis of that disease with the molecular defect of disturbed fibril formation due to the altered skin collagen-glycosaminoglycan equilibrium.