This document summarizes research on casual sex and well-being. It finds that whether casual sex is positively or negatively related to well-being depends on two factors: 1) The motivation behind the casual sex encounter (autonomous vs. non-autonomous motivation) and 2) An individual's level of sociosexuality. When casual sex is motivated by autonomous reasons and among individuals higher in sociosexuality, it is associated with greater well-being, whereas non-autonomous casual sex relates to lower well-being. Authenticity in casual sex encounters and relationships is important for buffering against distress and enhancing well-being.