Patients with coeliac disease are at greater risk than the general population for the development of malignant neoplasms, particularly lymphomas. Of 259 histologically confirmed malignancies in 235 patients with histologically proven coeliac disease, 133 were malignant lymphomas, the predominant histological type being malignant histiocytosis and the commonest site of this lesion the small intestine. Patients with coeliac disease also have a greatly increased risk for the development of small-intestinal adenocarcinomas. Among 116 invasive non-lymphomatous malignancies there were 19 small-intestinal adenocarcinomas, compared with 0 . 23 expected from national cancer registrations adjusted for sex and age. There were also more oesophageal and pharyngeal squamous carcinomas than expected.