Pituitary apoplexy is a rare but life threatening condition caused by sudden haemorrhage or infarction of the pituitary gland. Potential precipitating factors in the occurrence of acute pituitary apoplexy in 30 consecutive patients were identified and compared with the clinical characteristics and outcome of patients with and without associated factors. Six patients had a previously known pituitary adenoma. All patients complained of severe headaches, associated with neuro-ophthalmological symptoms and signs in 83% and altered mental status in 30%. Potential risk factors were identified in nine patients (30%). When there was an associated factor, the clinical presentation was no different than in patients without such factors although altered mental status may be more frequent in patients with associated diseases. In these patients, the visual prognosis was worse and the diagnosis was more difficult to establish. Acute pituitary apoplexy is unpredictable and should be considered in any patient with abrupt neuro-ophthalmological deterioration associated with headache. Patients with pituitary apoplexy often have an associated disease that confounds recognition and treatment despite a typical presentation.