Celiac disease (CD) has a wide range of clinical presentations and is being diagnosed with increasing frequency in patients in the 4th and 5th decades of life. The diagnosis of CD is confirmed by a combination of clinical, serological, and morphological findings associated with a response to a gluten-free diet. In small-bowel mucosal biopsy specimens, abnormalities range from minimal (increased villous intraepithelial lymphocytes only) to severe (complete villous blunting with crypt hyperplasia). Recognition of CD is important because appropriate therapy of this condition will obviate the risk of its severe complications.