Because individuals high on hostility may be at risk for alcohol abuse due to serotonergic dysfunction and greater reactivity to stress, we examined the effects of acute dietary tryptophan enhancement and stress on mood and craving for alcohol in low-hostile (LoH) and high-hostile (HiH) individuals. Methods: Thirty-four LoH and 33 HiH heavy social drinkers [selection based on the Hostility scale from the Buss and Perry Aggression Questionnaire (1992)] received either tryptophan-enriched or control diet and underwent a stress-induction procedure. Trait differences between the two hostile groups were explored using personality, anxiety, and depression questionnaires. Mood, craving for alcohol, and salivary cortisol levels (CORT) were measured before and after tryptophan and after stress-induction. Heart rate (HR) was measured during stress-induction. Results: HiHs compared to LoHs scored higher on the depression and anxiety trait scales as well in the character dimension Harm Avoidance and reported more of stress exposure over the past month. They also showed more negative mood and higher craving for alcohol. Diet alone did not produce any subjective or physiological effects. Stress increased CORT, HR, negative mood, and craving for alcohol. HiHs displayed higher CORT increase and lower cardiovascular reactivity in response to stress compared to LoHs. Opposite to the predictions, tryptophan enhancement selectively facilitated stress-induced increase in craving in the HiHs. Conclusion: Among heavy drinkers HiHs report higher craving for alcohol and show greater reactivity to stress as measured by CORT and negative mood. The effects of stress on craving in HiHs may be mediated by a serotonergic mechanism.