Nuclear androgen receptors (Arn)were measured in the pituitaries and hypothalami of adult male golden hamsters which had been injected with a long-acting preparation of bromocriptine or had pituitaries from adult females transplanted under the renal capsules. Treatment with bromocriptine markedly reduced pituitary Arn and plasma prolactin levels without altering plasma testosterone levels or hypothalamic Ar N. Ectopic pituitary transplants did not affect Arn in either the pituitary or the hypothalamus. These findings suggest that normal rates of prolactin synthesis and/or secretion may be required for maintenance of Arn in the pituitary of adult male hamsters.