This study will evaluate members in families with a history of small bowel carcinoid cancer to study the natural history of those family members that have the disease, determine ways to improve early detection by performing surveillance on those at risk but without disease and to identify the gene(s) that may cause the tumors. Familial carcinoid tumors usually originate in hormone-producing cells that line the small intestine or other cells of the digestive tract. The tumors are slow-growing and usually take many years before they cause symptoms. It is known that these tumors occur more often in some families and are then passed from one generation to the next by inherited genes. Members of families, including all siblings and offspring in which two or more immediate blood relatives have had small bowel carcinoid tumors are eligible for this study. In some cases unaffected spouses of family members diagnosed with carcinoid cancer are also requested to participate by donating a sample of blood only. Participants undergo a medical evaluation every 3 years during a 3- to 5-day hospital stay at the NIH Clinical Center. All participants have a personal and family medical history obtained and undergo a physical examination, blood and urine tests. People who already have a small bowel carcinoid tumor or are at risk of developing a carcinoid tumor have some or all of the following procedures to determine the presence of carcinoid tumor and its (omit next two words- location or) spread to other areas of the body: * Video Capsule Endoscopy: Visualization of the gastrointestinal tract by ingesting a disposable, "vitamin-pill sized" video capsule that has its own camera and light source. * CT of the chest abdomen and pelvis with oral and IV contrast : X-ray examination of the chest, abdominal and pelvis organs. * 18 FDOPA Positron emission tomography (PET) with CT for localization: Nuclear imaging scan to look at tumor activity. * MRI Liver with contrast - to determine if disease has spread to liver * Gallium 68 PET/CT-limited to individuals that have residual tumor. * Clinical and research blood work Should mid gut carcinoid tumors be found every participant will be assisted in determine what the best course of treatment will be for them.