The effect of pretreatment with the gonadotropin releasing hormone (GnRH) agonist D-Trp6-LHRH (Decapeptyl) on platelet serotonin transporter in women undergoing assisted reproductive treatment (ART) was investigated and compared with women treated with human menopausal gonadotropin (Pergonal). The study group (n = 10) was exposed for 12 days to 3.2 mg Decapeptyl C.R. while a comparison group (n = 9) was exposed to 11 days of human meno-pausal gonadotropin (Pergonal). All patients were assessed with the Hamilton depression and anxiety scales before and after treatment, and platelet and plasma samples were collected at the same time points. Plasma levels of estradiol, progesterone. FSH and LH were determined by radioimmunoassay (RIA). Platelet serotonin transporter was labeled using high affinity [3H]imipramine binding. The GnRH analogue induced ovarian suppression as reflected by low plasma estradiol levels, while Pergonal administration induced ovarian stimulation. An elevation in the Hamilton depression and anxiety scale scores was observed in the Decapeptyl treated group; this mood alteration was associated with a significant decrease (19%, P < 0.05) in the density (Bmax) of platelet [3H]imipramine binding sites. No significant change was observed in the Bmax of the Pergonal treated group. These results indicate that ovarian suppression (menopausal-like state) in young women is associated with depressed and anxious mood and decreased serotonin transporter density.