In all, 39 participants (19 male, 20 female) were classified as either happy (n = 19) or unhappy (n = 20) with a relationship. Baseline salivary cortisol was measured. Participants imagined (for a 5-min duration) scenes typical of their relationship, and salivary cortisol was measured again. Participants in unhappy relationships had higher cortisol reactivity (indicating higher stress) following the imagery. Cortisol reactivity was predicted by relationship variables (high love and liking for the partner, high happiness with the relationship) and personality variables (high forgivingness, low trait anger). Personality had an indirect effect through the relationship variables. Physical health was predicted by personality variables. Mental health was predicted by both personality and relationship variables. Implications of these results for counseling health psychology are discussed.