The quality of romantic relationships and their associations with both partners' personality traits and social networks were studied in 100 younger couples. The similarity of partners was modest with respect to personality traits, and moderate to large with respect to the perceived quality of the partner relationship and their social networks. While similarity in personality was unrelated to relationship quality, dyadic analyses showed that one's perceived quality of relationship was better predicted by one's own personality (i.e. actor effects) than by the personality of one's partner (i.e. partner effects). Moreover, relationship quality could to some extent be predicted by the quality of the social network once the personality traits of each partner were controlled. Results are discussed from a transactional view of personality and relationships. Copyright © 2004 John Wiley & Sons, Ltd.