The LH [lutropin] response to LHRH [luliberin] and the TSH [thyrotropin] and PRL [prolactin] response to TRH [thyroliberin] were examined in spontaneously hypertensive rats and normotensive control Wistar rats to determine if the pituitary response to these releasing hormones was altered in the hypertensive rats. Although basal levels of LH were similar in the 2 groups of rats, the LH response to LHRH was significantly less in the hypertensive rats than in the normotensive controls. The spontaneously hypertensive rats had higher basal levels of TSH and PRL and significantly greater TSH and PRL responses to TRH. The hypothalamo-pituitary axis was apparently altered in the spontaneously hypertensive rat.