Patients with celiac disease and dermatitis herpetiformis have circulating antibodies to reticulin and endomysium, the 'extracellular matrix' components as defined by their detection on rodent and primate tissues, respectively. Because both types of antibodies occur in both forms of gluten-sensitive enteropathy, studies were conducted to determine if the two types of antibodies can be distinguished by species and organ specificity. The results of these studies indicate that distinct endomysium-specific and reticulin-specific antibodies can be found and that these differ in their species specificity; i.e., endomysium antigen occurs in primate and not in rodent tissues while the reticulin antigen occurs in rodent and not in primate tissues. However, the activity of both endomysium and reticulin antibodies demonstrates similar tissue distribution, in that both react to antigens associated with gastrointestinal smooth muscles, peritubular and periglomerular areas of the kidney, and sinusoidal and periportal areas of the liver. Also, both antigens seem to be present in sheep and goat tissue. These studies indicate that the antigens reactive with endomysial antibodies are distinct from those reactive with reticulin antibodies.