The density of jejunal intra-epithelial T cells expressing the gamma/delta form of the T-cell receptor is known to be increased in coeliac disease, the significance of which remains a mystery. The expression of the gamma/delta T-cell receptor in the jejunum of patients with dermatitis herpetiformis, coeliac disease, treated and untreated, and controls were studied. Expression of the gamma/delta T-cell receptor was significantly increased in patients with dermatitis hepetiformis (P < 0.0005) and in both untreated (P < 0.0005) and treated coeliac patients (P < 0.05) compared with controls. There were significant correlations between the indices of enteropathy, enterocyte height (P < 0.005) and villous height/crypt depth ratio (P < 0.0001), and expression of the gamma/delta T-cell receptor in the jejunum of all the patients. This argues against the hypothesis that gamma/delta T-cells have a fundamental role in the aetiology of gluten-sensitive enteropathy. It suggests that gamma/delta T cells may be involved in the effector arm of the mucosal immune response to cereal peptides in susceptible individuals.