Celiac disease, or gluten-sensitive enteropathy, is defined as a state of heightened immunologic responsiveness to ingested gluten (from wheat, barley, or rye) in genetically susceptible individuals. Ingestion of the offending proteins leads to inflammation and intestinal mucosal damage, which may result in a spectrum of gastrointestinal symptoms, nutritional abnormalities, and systemic complications ranging from anemia and osteoporosis to secondary autoimmunity and malignancy. The genetic influence in the pathogenesis of celiac disease is indicated by its familial occurrence. Celiac disease does not develop unless a person has alleles that encode for human leukocyte antigen DQ2 or DQ8 proteins. The clinical picture of celiac disease has changed considerably during the past 30 years. Diarrhea, which was the presenting symptom in > 90% of celiac disease patients before 1981, is now the chief complaint in < 40%. In contrast, the increased frequency of atypical celiac disease presentations, including anemia and bone disease, is revealed by the widespread availability of serologic testing. An association between celiac disease and autoimmune disorders, such as type 1 diabetes, autoimmune thyroid disease, and Sjögren's syndrome, has been well documented. The tissue transglutaminase immunoglobulin antibody and the endomysial immunoglobulin antibody are the most sensitive and specific serologic tests, respectively, for identifying individuals who need to undergo an intestinal biopsy. If the suspicion of celiac disease is high, intestinal biopsy should be pursued even if serologic tests are negative. The gold standard for the diagnosis of celiac disease is a small bowel biopsy showing villous atrophy. The treatment for celiac disease is lifelong adherence to a gluten-free diet (GFD). Despite the proven benefits of the GFD, it can be exceedingly difficult to completely avoid gluten-containing foods, and adherence to a GFD is estimated to be only 45% to 80%.