In two of eight premenopausal women with somatotropic adenomas, galactorrhea was the earliest clinical feature, associated in one patient with amenorrhea. These two patients did not have clinically evident acromegaly. Mean basal serum GH levels were elevated and did not decrease after glucose ingestion. Both patients had modest hyperprolactinemia. Histological and immunocytological studies of the adenomas showed numerous adenomatous somatotropic cells and some alpha-subunit- and PRL-containing cells. In these patients, the origin of the hyperprolactinemia was not clear. In one patient, elevated GH secretion was probably responsible for the galactorrhea, since it disappeared after surgical treatment despite persistence of hyperprolactinemia. In conclusion, galactorrhea, isolated or associated with amenorrhea, can be the only clinical manifestation of a somatotropic adenoma.