The authors studied, in adult male and female rats the effect of one or repeated injections of chlorpromazine on adrenal secretion of corticosterone and pituitary secretion of prolactin. 2. Injections of chlorpromazine increased plasma corticosterone, plasma and pituitary prolactin. 3. The discussion of the results was correlated to the brain catecholamines postulated to be neurotransmitters involved in the control of corticotropin and prolactin pituitary secretion.