The present study was undertaken to determine the effects of androgen implants in the preoptic area-suprachiasmatic nucleus (POA-SCN) on catecholamine turnover in the POA-SCN and the medial basal hypothalamus (MBH) in orchidectomized rats. Bilateral implants of testosterone (T) or dihydrotestosterone (DHT) in the POA-SCN of orchidectomized rats did not affect serum concentrations of LH and FSH or the turnover of dopamine (DA) and norepinephrine (NE) in the MBH. In the area surrounding the implants in the POA-SCN, T and DHT decreased dopamine turnover by 67 and 37%, respectively, without influencing the POA-SCN norepinephrine turnover. These results indicate (i) that T implants in the POA-SCN selectively depress POA-SCN dopamine turnover, (ii) that this effect of T may occur following its conversion to DHT, and (iii) that these androgen effects probably do not mediate the negative feedback action of T on gonadotropin secretion.