Forming long-term intimate relationships constitutes an important aspect of human nature. Within the context of an evolutionary theoretical framework, the current research has attempted to investigate what motivates people to keep an intimate relationship. Using a combination of qualitative research methods in a sample of 131 Greek-speaking participants, 58 reasons that motivated individuals to keep their intimate relationship were identified. Using quantitative research methods in a sample of 789 Greek-speaking participants who were in an intimate relationship, these reasons were classified (...) in nine broad factors and two broader domains. Having a supporting and compatible partner with whom one shares similar goals, and with whom one has good sex and a strong emotional attachment, were rated among the most important factors motivating participants to keep their relationship. Moreover, as indicated by the domain means, participants were more strongly motivated to keep their intimate relationship if their partners had desirable attributes, such as providing them with support, and less so by their own attributes, such as fear of loneliness. Significant effects of sex, age, marital status, presence of children, and years in a relationship were found for several factors. (shrink)