A 66–year–old man suffered from a drug–resistant, leftsided headache with autonomic signs, triggered by the supine position. The acromegalic facies initially suggested a possible increase in basal plasma levels of GH, but routine haematological controls excluded abnormal values of GH. Cerebral and facial CT scan and MRI did not detect any alterations in the nasal sinuses, except for a mucous cyst. Surgical ablation of the cyst did not alleviate the pain. Further endocrinological tests demonstrated an increase of IGF–1 (somatomedin C), and another MRI scan of the sellar region confirmed the presence of a pituitary macroadenoma on the left paramedian side. After an initial improvement of the symptomatology due to trans–sphenoidal ablation of a benign GH–producing macroadenoma, the headache worsened again. Pain was well correlated with the increased plasma levels of IGF–1. The patient died suddenly for myocardial infarct.