One hundred and seventy patients with endocrine abnormalities, 29 males and 141 females, were studied by computerized tomography (CT) scanning of the pituitary and by pituitary hormone assays including basal and stimulated hormone concentrations in the blood. Pituitary macroadenoma was observed in 40 of the 170 patients, microadenoma in 49, primary empty sella in 46, secondary empty sella in 25, including 20 of the 40 patients with macroadenoma after surgical removal or radiation therapy of the tumor. Suprasellar tumor was present in four patients. In 23 women with menstrual abnormalities and 3 men with impotence and hyperprolactinemia, the results of CT scanning were normal. Of the 40 patients with macroadenoma, 24 presented with a hyperfunctioning syndrome (acromegaly or hyperprolactinemia). Among the 49 patients with microadenomas, 46 had the amenorrhea-galactorrhea syndrome, one male presented with acromegaly and one with Cushing's disease, and one female also had Cushing's disease. Primary empty sella was associated with the amenorrhea-galactorrhea syndrome in females and impotence in males. Only four female patients demonstrating an empty sella were asymptomatic. Distinctive biochemical findings were identified in certain groups of patients with different pituitary pathologic features. CT scanning was found very useful in the assessment of the size of the tumor, its suprasellar or parasellar extension and response to therapy, and in differential diagnosis of tumor and empty sella. Disappointing results were obtained in patients with endocrine abnormalities and normal results of CT scanning, and in patients following surgical treatment for a pituitary tumor, when the identification of recurrent tumor was impossible from a single examination. It is concluded that CT scanning is the most advanced technique in the diagnosis of anatomic pituitary abnormalities and it should replace the traditional invasive diagnostic procedures.