The rate at which radiolabelled liquid and semisolid meals leave the stomach following oral ingestion is a routine measure of gastric function, usually performed to exclude gastroparesis, and less often to assess symptoms that may be the result of abnormally accelerated gastric emptying associated with the clinical syndrome of ‘dumping’. Tc-99mO4 is complexed with a semisolid meal, such as mash, and consumed by the patient. Dynamic imaging or sequential image acquisition at 5 min intervals over 60 min is then undertaken. Normally, less than 50% should be retained at 60 min. Tc-99m-labelled  liquid leaves the stomach more rapidly than a semisolid meal and is often used in conjunction with a semisolid study. A liquid study is preferred for the detection of gastro-oesophageal reflux, especially in paediatrics and for the diagnosis of aspiration syndrome.