Pre-Cushing's syndrome (PCS) is defined as an overproduction of cortisol by an adrenal adenoma, without physical changes on clinical examination. Three patients with PCS were recently diagnosed among 21 consecutive patients suffering from adrenal 'incidentaloma'. All patients showed nonsuppression of serum and urinary cortisol following 2 and 8 mg of dexamethasone (DXM), and suppressed or normal baseline plasma ACTH. Unilateral uptake of radiolabelled iodocholesterol, which persisted after DXM, was uniformly present. The authors review 36 patients with PCS previously reported. This entity probably constitutes a transition from classic 'nonfunctional' adrenal adenoma to cortisol-producing adenoma. Uniform guidelines in the management of PCS cannot yet be given, but surgical intervention is usually required to prevent the development of long-term complications of subtle corticoid excess.