Serum growth hormone (GH) and luteinizing hormone (LH) levels were determined by homologous radioimmunoassay in 8 to 10-week-old domestic white turkeys treated by intraperitoneal injection of agents that alter serotonergic activity. The serotonin, 5-hydroxytryptamine (5-HT) precursor, 5-hydroxytryptophan (5-HTP), at doses of 80 and 150 mg/kg, produced a dose-related elevation in serum GH (P = .09) and no change in serum LH (P = .30). Administration of fluoxetine (10 mg/kg), a 5-HT reuptake blocker, produced no change in serum GH or LH. When fluoxetine injection preceded the administration of a nonstimulatory dose of 5-HTP, an elevation in GH was observed, but again no change in LH level was evident. Stimulation of postsynaptic 5-HT receptors with quipazine (.5 to 10.0 mg/kg) resulted in a similar elevation in GH; persistence of the effect was dose dependent. Quipazine administration had no influence on serum LH levels. Administration of methysergide (10 or 25 mg/kg), a 5-HT antagonist, induced no change in either serum GH or LH levels. Serotonergic input appears to stimulate GH release and has no apparent influence on LH release in young turkeys.