The objectives of this study were to analyze the characteristics of headache in patients with pituitary adenoma and to investigate the mechanisms involved. Fifty-one patients (27 females and 24 males) with pituitary adenoma were examined. Nineteen (37.3%) of these patients (13 females and 6 males) had headache preoperatively. Most commonly, the headache was generalized (42.1%); overall headache was more frequent in the anterior half of the head (84.2%). Seventeen (89.5%) patients had bilateral headache. Headache was usually described as head heaviness (57.9%) and continuous (57.9%). Pulsating headache and dull pain were only reported by the female patients and were mostly intermittent. The mean age of patients with headache was younger than that of those without headache. Headache was more prevalent in patients with a prolactin-secreting adenoma (57.1%). There were no correlations between visual disturbances, hypopituitarism, tumor size, or cavernous sinus invasion and headache. Hemorrhagic pituitary adenoma in 4 (57.1%) of 7 patients did not always contribute to headache. The headache was improved after surgery in 14 (73.6%) of the 19 patients. In the male patients who survived postoperatively (5 of 6), headache was improved.