Authors analyzed retrospectively the incidence of pituitary apoplexy in a series of 799 pituitary adenomas with respect to the long term follow-up of the patients. Focal vascular abnormalities in histological specimens of tumours, regarded as morphological suggestion of past apoplexy (haemorrhage, ischaemic infarction or necrosis), were established in 113 out of 783 surgical cases (14.4%). Acute clinical onset, justifying the clinical diagnosis of pituitary apoplexy, occurred in 39 patients only (5% of the whole series), 19 of them were subjected to urgent surgical decompression due to severe neurological deficit. The haemorrhagic character of apoplexy was established in most cases requiring immediate surgery. The detailed clinical picture of this condition and its management are discussed with respect to the long term prognosis. On this basis the authors suggest the necessity of surgical treatment in every case of pituitary apoplexy, taking into account not only neurological recovery, but also endocrine and oncological aspects of the disease. The observation that pituitary apoplexy may be a "marker" of tumour invasiveness (even in small, "enclosed" adenomas) is highlighted.