Celiac disease is a small intestinal immune-mediated enteropathy precipitated by exposure to gluten, a protein complex in the cereals wheat, barley and rye, in genetically susceptible people. Once considered an uncommon disorder restricted to children of European descent, it is now known to be one of the most common chronic diseases encountered in the Western world, with a serological prevalence of 1% that can be diagnosed at any age. Since it is so common much co-morbidity comprising malignant and non-malignant conditions will occur in association. Malignant complications particularly lymphoma were first described over 50 years ago but the natural history and how commonly these occurred were unknown until relatively recently. Similarly, many non-malignant conditions were known to occur but initially the risks were unclear. It was not until the frequency of coeliac disease could be determined accurately in the community and population-based studies of morbidity and mortality in coeliac disease patients carried out in defined cohorts that these questions could be answered. My research into these aspects of coeliac disease began in 1971 and a body of 35 of my publications spanning the years 1974 to 2018 on the morbidity and mortality of the disorder are presented in this thesis. I have introduced my research findings at many international and national meetings and these data have been influential in shaping the research agenda of other workers. One of my papers (Publication 9) published in Gut in 1989, was the most cited of all papers which appeared in the journal for that year. To date it has been cited 1122 times. Information exists for 24 papers presented here and for these the total number of citations stands at 3,887. This excludes references to book chapters. Anecdotal evidence indicates frequent mentions in lectures and clinical practice.