The traditional definition of coeliac disease is inadequate because it includes only patients with abnormal small intestinal morphology. Gluten sensitivity is a systemic disorder whose common factor is an immune response to gluten in the context of the susceptible 'coeliac' HLA haplotype and possibly environmental triggers. Gluten sensitivity embraces traditional coeliac disease as well as subjects with normal small bowel morphology including latent coeliac disease, dermatitis herpetiformis, and symptomatic gluten intolerance. The diagnosis of gluten sensitivity and coeliac disease are not mutually inclusive. Small intestinal biopsy and clinical criteria are essential in diagnosing classical coeliac disease. IgA endomysial antibody is valuable in identifying gluten sensitivity and has particular value as a screening test. Serology should include total IgA levels to exclude selective IgA deficiency, a potential cause of false negative IgA endomysial antibody. A combination of histology, serology and clinical criteria will identify most cases of coeliac disease and gluten sensitivity.