The case history of a 54-year-old male suffering from pituitary macroadenoma with suprasellar extension is reported. A TRH-test with 200 micrograms i.v. was followed by severe headache and vomiting after 60', and by development of ophthalmoplegia on the following day. Hyperdens patches on the CT scan showed haemorrhage into the tumor. A chromophobic adenoma with macroscopic and histological signs of haemorrhage was removed via the transsphenoidal route. In the postoperative period the ophthalmoplegia gradually disappeared but central hypoadrenia and hypothyroidism occurred. This is the second case in the literature showing that TRH alone and in a low dose may cause pituitary tumor apoplexy. It is concluded that TRH-testing is a risk for the patient with pituitary apoplexy. If, due to the size of the tumor the patients have to be operated on in any case, and the test is not of essential diagnostic value, the TRH-test should be done only in selected cases. Its use in the postoperative evaluation however is without risk for the patients.