Five cases of pituitary apoplexy occurring in patients with pituitary tumours are described. This uncommon condition is characterized by headache, sudden loss of vision, alteration in the level of consciousness, and usually an abnormal cerebrospinal fluid. The whole picture may be complicated by endocrine dysfunction. The diagnosis is strengthened by a radiologically abnormal pituitary fossa and confirmed by the operative finding of haemorrhagic necrotic tissue. Surgical decompression under steroid cover offers the only hope of restoration of vision. Frequent postoperative follow-up is obligatory.