1. An experiment was conducted to investigate the effects of feeding supplemental tryptophan during the two weeks before market on growth, mortality during transportation, meal quality and brain neurotransmitter concentrations in male turkeys. 2. Brain serotonin, 5-hydroxyindoleacetic acid and norepinephrine concentrations were increased dose-dependently with 1.0, 2.0 and 3.0 g/kg supplemental dietary tryptophan. 3. Supplemental dietary tryptophan had no effect on body weight gain, food intake, food efficiency or mortality. 4. Carcase and individual thigh weights were significantly heavier in those birds fed 1.0 g/kg supplemental tryptophan.