Celiac disease is an autoimmune disorder of the gastrointestinal tract. It is triggered by exposure to dietary gluten in genetically susceptible individuals. Gluten is a storage protein in wheat, rye, and barley, which are staples in many American diets. Celiac disease is characterized by chronic inflammation of the small intestinal mucosa, which leads to atrophy of the small intestinal villi and subsequent malabsorption. The condition may develop at any age. Intestinal manifestations include diarrhea and weight loss. Common extraintestinal manifestations include iron deficiency anemia, decreased bone mineral density, and neuropathy. Most cases of celiac disease are diagnosed in persons with extraintestinal manifestations. The presence of dermatitis herpetiformis is pathognomonic for celiac disease. Diagnosis is supported by a positive tissue transglutaminase serologic test but, in general, should be confirmed by a small bowel biopsy showing the characteristic histology associated with celiac disease. The presence of human leukocyte antigen alleles DQ2, DQ8, or both is essential for the development of celiac disease, and can be a useful genetic test in select instances. Treatment of celiac disease is a gluten-free diet. Dietary education should focus on identifying hidden sources of gluten, planning balanced meals, reading labels, food shopping, dining out, and dining during travel. About 5% of patients with celiac disease are refractory to a gluten-free diet. These patients should be referred to a gastroenterologist for reconsideration of the diagnosis or for aggressive treatment of refractory celiac disease, which may involve corticosteroids and immunomodulators.