The role of a procedure depends not only on its own capabilities but also on a cost/effective comparison with alternative techniques giving similar information. Starting from the definition of emergency as a sudden unexpected occurrence demanding immediate action, the role of nuclear medicine (NM) is difficult to identify if it is not possible to respond 24 h a day, 365 days a year, to clinical demands. To justify a 24 h NM service it is necessary to reaffirm the role in diagnosis of pulmonary embolism in the spiral CT era, to spread knowledge of the capabilities of nuclear cardiology in reliably diagnosing myocardial infarction (better defining admission and discharge to/from the emergency department), to increase the number of indications. Radionuclide techniques could be used as first line, alternative, complementary procedures in a diagnostic tree taking into account not only the diagnosis but also the connections with prognosis and therapy in evaluating cerebral pathologies, acute inflammation/infection, transplants, bleeding, trauma, skeletal, hepatobiliary, renal and endocrine emergencies, acute scrotal pain.