Romantic relationships contribute to individual well-being and, as such, to the prosperity and stability of communities as well (see Berscheid & Reis, 1998). As a consequence, a great deal of research has been conducted in order to determine the factors that affect relationship quality. While human sexuality clearly plays an important role in the development and maintenance of romantic relationships, relatively little research has been done to examine the connections between sexual behaviour and relationship quality directly (see Miller, 2012). Despite the dearth of direct empirical investigations to draw upon, a close reading of relationship theory and related research indicates several ways that relationship quality may be sustained and improved through modification of couple sexual behaviour. In the early stages of romantic relationships, partners typically experience a heightened sense of passion for one another, manifested in strong feelings of attraction, a yearning for togetherness, high sexual desire, and frequent sexual communion. Unfortunately, this characteristic longing typically begins to wane over time (Acker & Davis, 1992; Christopher, & Sprecher, 2000). As passion declines, coital frequency and relationship satisfaction also decrease notably (Call, Sprecher, & Schwartz, 1995, Tucker & Aron, 1993). While declines in these aspects of relationship quality are common, they do not occur in all couples, and it is possible that they can be reversed or minimized. According to Aron and Aron (1986), decline in relationship quality is partially driven by habituation to the novelty of a new relationship, or the onset of boredom. To revitalize relationships, they suggest that couples participate in novel and exciting activities together, in the hopes that partners will come to associate the positive affect and heightened arousal generated during these activities with improved relationship quality (Aron, Norman, Aron, McKenna, & Heyman, 2000). There is some evidence for these assertions in correlational studies which have found that couples who engage in more shared activities have higher relationship quality (Aron et al., 2000), and greater relationship longevity (Hill, 1988), than couples who report less shared activity. Experimental research has also found that couples asked to participate in shared novel tasks subsequently report higher relationship quality than couples asked to participate in shared pleasant or mundane tasks (Aron et al., 2000; Reissman, Aron, & Bergen, 1993). Intimacy in couples, which involves feelings of closeness, understanding, and strong positive regard for one-another, is also believed to increase through shared experiences in novel situations (Clark & Reis, 1988; Reis & Shaver, 1988, Reis & Patrick, 1996). Provided that new information acquired about one’s partner during the experience is met with positive responses, intimacy between partners deepens. According to Baumeister and Bratslavsky (1999), intimacy and passion are inexorably linked, in that passion is the experiential perception of changes in intimacy (p. 49). This may explain the different time courses of intimacy and passion: while low at the outset of new relationships, intimacy increases rapidly in the early stages of relationships, when passion is high (Baumeister & Bratslavsky, 1999). Eventually however, intimacy plateaus as there are fewer opportunities to learn new things about each other, and passion recedes. This perspective echoes the observed lack of strong mutual sexual desire among long-term couples with high stable levels of intimacy (Perel, 2009). Interestingly, while theory and research concerning the enactment of shared novel behaviours have clear implications for the impact of shared novel sexual behaviours on relationship functioning, the impact of experimentally prescribed novel sexual behaviour on specific aspects of relationship quality has not been measured. Instead of employing experimental manipulations that approximate naturally occurring instances of novelty, studies have traditionally created artificial laboratory situations to examine the impact of nonsexual novelty on relationship quality (e.g. asking couples to complete an obstacle course while tied together; see Aron et al., 2000). As novel sexual behaviours constitute naturally occurring and intense instantiations of more general shared novel activities, the failure to examine the impact of novel couple sexual interactions represents a missed opportunity to test theory under conditions that have greater generalizability. The goal of this research is to investigate the theorized impact of novel sexual behaviours on different elements of relationship quality in established romantic relationships. The specific purpose of this research is to test the hypothesis that the introduction of novel sexual behaviours in long-term heterosexual couples will positively impact perceptions of intimacy, passion, and sexual and relationship satisfaction. The results of this research will expand the foundation of theoretical knowledge concerning effects of shared novelty on the couple relationship, and provide a wealth of information concerning the particular impacts of shared novel sexual behaviours on relationship processes and outcomes.