Neoplasms constitute the major complication of coeliac disease, and high-grade T-cell lymphoma of the small intestine (enteropathy-associated T-cell lymphoma) is the most common neoplasm in this category. HLA genotyping indicates that in patients with enteropathy-associated T-cell lymphoma have the coeliac disease associated DQA1*0501, DQB1*0201 phenotype, although additional HLA-DR/DQ alleles may represent risk factors for lymphoma development. Molecular biological and immunohistochemical studies have shown that the intestinal mucosa distant from the tumour contains clonal populations of small T cells, often of the same clone as the high-grade T-cell lymphoma. These findings suggest that enteropathy-associated T-cell lymphoma arises in the setting of coeliac disease and evolves from reactive intraepithelial lymphocytes through a low-grade lymphocytic neoplasm to a high-grade tumour, which is usually the cause of the presenting symptoms. Most cases of chronic ulcerative enteropathy (ulcerative jejunitis) are probably part of the same disease process. If the ulceration occurs at a time when the neoplastic T-cells are of a low grade, morphological recognition of tumour cells in the ulcers may be impossible. Carcinoma of the pharynx and oesophagus, and adenocarcinoma of the small intestine, are increased in frequency in patients with coeliac disease. The increased risk of carcinoma of the oesophagus may be related to vitamin A deficiency. A number of reports have indicated an increased prevalence of various types of chronic hepatitis in patients with coeliac disease, but no coherent view of the cause of this association has emerged. Similarly, patients with coeliac disease have been reported to have various forms of fibrosing lung disease of uncertain causation. In recent years, there have been several reports, mainly from Italy, of a syndrome of epilepsy and bilateral brain calcification occurring in coeliac patients. The pathogenesis of this condition is not known and its prevalence in other communities is uncertain. Splenic atrophy occurs frequently in patients with coeliac disease and is related to the severity of the disease and degree of dietary control. Splenic atrophy predisposes to infection with capsulated bacteria, although mortality studies indicate that infection with these organisms is not a major cause of death in patients with coeliac disease.