Pituitaries removed from ovariectomized adult rats were maintained for 18 weeks in organ culture using three different culture media. Gonadotropin secretion was assessed by RIA and was correlated with the histological features of the cultures. In medium favoring prolonged survival of the cultures, LH content of the medium fell to a low level within a few days. In the same cultures, FSH production initially decreased before increasing and leveling at a plateau which persisted until the end of the culture period. Cultures in medium unsuitable for long term survival of pituitary tissue displayed a similar decrease in LH production along with a gradual fall of FSH. It was concluded that contrary to LH, FSH may be secreted autonomously by pituitaries removed from hypothalamic control, provided that culture conditions are adequate for survival of gonadotropes.