A man had left-sided atypical clusterlike headache for II years before he developed symptoms and signs consistent with acromegaly. Preoperative evaluation revealed raised levels of somatomedin C and growth hormone. An MR indicated a left-sided intrasellar mass measuring 8 x 7.5 x 10 mm. He underwent surgery and microscopy confirmed the diagnosis of a benign hypophyseal adenoma. Postoperatively, the acromegalic features regressed, and for the last 4 years the patient has been completely free from headache attacks. On pharmacological testing of the pupillary response to 19 and 5% phenylephrine and 2% tyramine solutions, there was no convincing evidence of persistent sympathetic dysfunction on the earlier symptomatic side.