The release of LH and FSH by male rat pituitary glands (P) or pituitary-median eminence (P-ME) units was studied in flasks and in a superfusion system. The amounts of both hormones secreted into the medium from P-ME units were higher than those from P alone. When the incubations were carried out in the presence of dopamine at a concentration of 2.5 μg/ml, there was no change in LH and FSH release by P, but the release of LH from P-ME unit was reduced. The inhibiting effect of dopamine was also observed in the superfusion of P-ME unit. Dopamine at a lower concentration of 0.25 μg/ml, did not alter the release of LH. The effect of dopamine was not blocked by estradiol at a concentration of 1 μg/ml medium. (Endocrinology93: 492, 1973)