Celiac disease is a very common autoimmune disorder caused by the ingestion of dietary gluten products in genetically susceptible persons. Its global prevalence is estimated around 1 %. However, the most cases are not diagnosed. Clinical presentation is widely variable with the involvement of various human systems. Besides a clinical picture (that is often non characteristic), the diagnosis is based on positivity of serological testing (tissue transglutaminase autoantibodies) and histological evaluation of small intestinal mucosa. The article presents a rational diagnostic approach to celiac disease. Key words: celiac disease - Marsh classification - tissue transglutaminase autoantibodies - villous atrophy.