The incidence of celiac disease has increased considerably during the last two decades. Celiac Disease is now diagnosed in adults at least as frequently as in children. A prevalence of about 1:200 seems reasonable in central Europe. Besides the typical symptomatic presentation, silent, latent and potential celiac disease are found. Oligo- to asymptomatic courses (silent celiac disease) are increasingly found in all age groups. Endomysial antibodies and tissue-transglutaminase antibodies are sensitive and specific for about 95% of celiac patients. However, the final diagnosis is only done by a - mostly endoscopical - biopsy from the distal part of the duodenum, demonstrating hyperplastic villous atrophy of the mucosa with increased numbers of intraepithelial lymphocytes. The biopsies should be classified histologically according to the modified Marsh criteria. Increased prevalence in family members (10 to 15%) and in associated diseases (e.g. diabetes mellitus) lead to the recommendation of active screening in populations at risk. Although the clinical symptoms are rather variable and different, the response to a lifelong strict gluten free diet is nearly 100%. So-called refractory celiac disease is very rare. There are numerous associated diseases as dermatitis herpetiformis, diabetes mellitus type I, thyroid and neurologic diseases. The most frequent complications are retardation of growth in childhood, early onset osteoporosis, and an increased risk of abortions. The most severe complication is intestinal lymphoma. Especially patients with late diagnosis and bad dietary adherence are at risk. A regular follow-up of patients, rather with antibody tests than with duodenal biopsies is recommended to test and secure dietary compliance.