Gastric emptying can be measured by three basically different means: Intubation -x-ray - Isotopes, X-ray methods may be neglected as they do not permit quantitative measurement of the exptying process. Intubation methods offer the advantage of exact determinations of emptying rates, but disadvantages are the limitation to liquid meals and patient discomfort. Radioisotopes can be used as marker both of liquid and solid foodstuffs with minimal patient discomfort. However problems often neglected wtih isotopes are reliability of their attachement to the marked meal and radiation dose to the probands. The most important indications of measuring gastric emptying is determination of alterations induced by peptic ulcer surgery and drugs.