Celiac disease is becoming an increasingly recognized autoimmune enteropathy caused by a permanent intolerance to gluten. Once thought to be a rare disease of childhood characterized by diarrhea, celiac disease is actually a multisystemic disorder that occurs as a result of an immune response to ingested gluten in genetically predisposed individuals. Screening studies have revealed that celiac disease is most common in asymptomatic adults in the United States. Although considerable scientific progress has been made in understanding celiac disease and in preventing or curing its manifestations, a strict gluten-free diet is the only treatment for celiac disease to date. Early diagnosis and treatment, together with regular follow-up visits with a dietitian, are necessary to ensure nutritional adequacy and to prevent malnutrition while adhering to the gluten-free diet for life. The purpose of this review is to provide clinicians with current updated information about celiac disease, its diverse clinical presentation and increased prevalence, the complex pathophysiology and strong genetic predisposition to celiac disease, and its diagnosis. This review focuses in detail on the gluten-free diet and the importance of intense expert dietary counseling for all patients with celiac disease. Recent advances in the gluten-free diet include food allergen labeling as well as the US Food and Drug Administration's proposed definition of the food-labeling term gluten-free. The gluten-free diet is complex and patients need comprehensive nutrition education from a skilled dietitian.