Cushing's syndrome includes all the clinical manifestations induced by chronic glucocorticoid excess. The endogenous Cushing's syndrome is rare, but its prevalence, although difficult to define, is much higher in populations at risk. Data suggest that early and effective management would reduce morbidity and mortality after correction of hypercortisolism. It is not recommended to widespread test for Cushing's syndrome but targeted screening is indicated especially in the following indications: facio-troncular obesity, hypercatabolism signs, pituitary and adrenal tumor. In case of potential but less specific manifestation of Cushing's syndrome (diabetes, hypertension, osteoporosis, hypogonadism…), but unusual for age, familial background, or severity, particular attention will be paid to the clinical examination to search for signs of modest hypercortisolism which may justify screening. The positive diagnosis of Cushing's syndrome is based on two stages approach with the first tests simple and sensitive, and the second tests more specific, with investigations to determine the cause following a positive diagnosis.