The effects of perphenazine on galactopoiesis were studied in 52 goats in the phase of declining lactation (September-December). At the beginning of September, perphenazine (1 mg) was stereotaxically implanted into the hypothalamus, sham-implantations being performed on control animals. After the operation milk yield decreased and stabilized at a new starting level in most animals of both groups. The average weekly milk yield of the sham-implanted goats gradually fell during the experimental period. This progressive decline in yield was greatly reduced if perphenazine had been implanted in the median eminence (ME). No galactopoietic effects were observed when the implantation was localized outside the ME.