The clinical appearance of celiac disease is diverse, often times uncharacteristic and may therefore be very difficult to diagnose. Furthermore, severe inflammation of the small bowel can be present without gastrointestinal symptoms. It is estimated that most subjects with celiac disease are not diagnosed. Yet, early diagnose is desirable, since celiac disease causes growth retardation in untreated children and is potentially cancer disposing. Thus, all patients should adhere to a strict gluten-free diet. The role of antibody testing and small bowel biopsy in celiac disease will be discussed. In the future, the development of new tests may allow screening of large populations.