The recently described IgA anti-endomysial antibodies (IgA-EmA) are directed against the intermyofibril substance of the smooth muscle, which may correspond either to a reticulin-like structure or a surface component of smooth muscle fibrils. These antibodies occurred in about 80% of sera of thirty-eight patients with dermatitis herpetiformis (DH), in about 70% of twenty-eight patients with coeliac disease and in about 20% of nine patients with other enteropathies. IgG class anti-gliadin antibodies (AGA) also occur in each of these diseases. Both antibodies were detected on monkey oesophagus by immunofluorescence. The IgA-EmA could not be detected in 122 control sera from patients with other gut or skin diseases, including fifteen cases with ulcerative colitis and fifteen cases with linear IgA bullous dermatosis (LABD). The presence and the titre of IgA-EmA and AGA paralleled the severity of the jejunal changes in patients with coeliac disease.