Fibroblast cultures were established by explant culture from upper and lower dermis of 7 normal donors and 10 patients with early progressive systemic sclerosis (PSS). Antibodies against collagens containing the A and B chains, collagens which occur largely in vascular structures, were isolated and used for immunofluorescence studies. Cultures from lower PSS dermis accumulated significantly more of these collagens than fibroblast cultures from upper PSS dermis or cultures from upper or lower dermis of normal skin. These data indicate that the collagens containing the A and B chains in early PSS lesions are produced by cells of vascular origin and support the concept that alterations in vascular tissue play a prominent role in the pathogenesis of PSS.