Pituitary cells synthesize various neuropeptides that influence pituitary hormone secretion. GH-releasing factor (GRF) may also be produced by normal or pituitary tumor cells. We examined GRF gene expression in pituitary tumors. Standard techniques for the analysis of GRF gene expression did not appear to be suitable. Highly sensitive reverse transcription coupled to polymerase chain reaction was used. Specimens of pituitary adenoma were obtained by transsphenoidal adenomectomy from six patients with acromegaly and three patients with no clinical evidence of pituitary hormone overproduction; non-functioning adenoma. Pituitary glands were collected at autopsy from three patients who died from nonendocrine disorders. A specific GRF gene transcript was detected in five out of six GH-producing pituitary adenomas, whereas this was not found in three separate specimens of nonfunctioning pituitary adenoma or anterior and posterior pituitary tissue. The data suggest that GRF is synthesized as an intrinsic product in human GH-producing pituitary adenoma.