IntroductionThe present study measured the daily correlates of sexual behavior in an ecologically valid context by relying on a daily diary approach. AimExamining the dyadic and multicomponent nature of sexual behavior is essential to create valid models of sexual responding that are better aligned with the day-to-day context of having sex in a relationship. Methods and Main Outcome MeasuresDuring 3 weeks, heterosexual couples completed, two times a day, an electronic diary to report on mood, own and perceived partner behavior, relational feelings (in the evening), sexual activity, physical intimacy, and masturbation (in the morning). This design allowed testing bidirectional temporal associations between daily context and different types of sexual behavior. ResultsPositive mood, displays of positive partner behavior, perceived positive partner behavior, and positive relational feelings predicted more sexual activity and intimacy in men, which then further increased their positive mood, perceived positive partner behavior, and positive feelings about the relationship on the following day. Women showed a similar pattern of predictors regarding sexual activity as men, though the effect of sexual behavior on next-day feelings and behavior was more relationship-oriented rather than affecting personal mood. Intimacy was related to almost all daily variables in women, but related only to own and perceived positive partner behavior and positive relational feelings the next day. Several partner effects also reached significance, and these were more influential in predicting male than female intimacy. Solitary sexual activity showed a different pattern of results than dyadic sexual activity, with men experiencing masturbation as negatively in the context of their relationship. ConclusionThese results confirm the regulatory function of sex and intimacy in maintaining a positive relational climate and indicate that the quality of the everyday relational context is important to get partners in the mood to act in a sexual way. Dewitte M, Van Lankveld J, Vandenberghe S, and Loeys T. Sex in its daily relational context. J Sex Med 2015;12:2436-2450.