Radionuclide studies of the gastrointestinal tract (GI) are used to measure GI function and to detect anatomic lesions such as Meckel's diverticuli. A variety of physiological and pharmacological interventions have been applied to both types of studies to gain a better understanding of GI function and to improve detection of disease. This article will review interventions useful in imaging the tubular GI tract. Discussed are the measurement of GI motility and function by gastric emptying and imaging studies for GI bleeding including the Meckel's scan. Interventions involving the hepatobiliary system are covered elsewhere in this issue.