The authors examined the relationship between 6 personality dimensions (Big Five personality factors and positive expressivity) and marital satisfaction in 132 distressed, treatment-seeking couples and 48 nondistressed couples. This study's focus on personality similarity in distressed couples, a population of interest to researchers and clinicians, is unique. Results suggest that higher neuroticism, lower agreeableness, lower conscientiousness, and less positive expressivity are tied to marital dissatisfaction. However, low overall levels of partner similarity were found on these variables. Furthermore, partner similarity on these variables did not independently predict relationship satisfaction. This suggests that nonpathological variations in these personality dimensions do not contribute to satisfaction, and that similarity between partners' personalities may not be closely tied to marital happiness.