This study examines the association between various domains of social network support and the long-term marital success of husbands and wives who had been married for an average of 20 years. We hypothesized that three domains of social network support (e.g., support related specifically to the relationship, affective overlap, and general personal support) would predict marital success. Overall, the findings suggest that social networks are influential in long-term marital relationships. For both husbands and wives, relationship-specific support predicted positive change in marital success from 1991 to 1994. Neither affective overlap nor personal support predicted marital success. This study underscores the significance of different domains of social support in long-term romantic relationships, the role of social support in predicting marital success, and the role of marital success in predicting social support. Couples function within social contexts, vulnerable to the influences and pressures of members of their social networks (Boissevain, 1974; Lewis, 1973; Milardo & Lewis, 1985; Ridley & Avery, 1979). Because of their importance for each spouse, these social influences can affect the quality and course of marital relationships. This study examines the connection between the influence of social networks and marital success among people in longterm marriages. Most previous research examines this connection using cross-sectional data or longitudinal data in which time intervals are just months apart; samples of dating partners or samples in which many of the spouses are in their early years of marriage; samples in which only one of the partners, rather than the couple, is in the relationship under study; or samples of college students. In contrast, the study presented here is longitudinal. It covers 3 years, focuses on long-term (1437 years) married couples, gathers data from both spouses rather than just one partner, and uses a sample recruited from the community at large. Before considering the association between marital relations and the broader social context, however, it is worthwhile to review the defining characteristics of social networks used in this report. A social network is a collection of people known by an individual. A psychological network is a specific type of social network composed of people in whom an individual is most likely to confide or place trust, and it typically includes parents, in-laws, other kin, and close friends. These are people who can alter an individual's definition of self by communicating their thoughts and ideas about the individual's actions to him or her. Those thoughts and ideas can influence the initiation, maintenance, and dissolution of romantic relationships (Surra, 1988). Two primary models have been proposed to account for the influence that networks exert on romantic relationships-the support model and the interference model (Milardo & Lewis, 1985). The support model asserts that network members help couples build feelings of satisfaction with their partners by validating their relationships (e.g., commenting about how nice a pair the couple makes), nurturing a sense of coupleness by inviting the pair to social events as a couple (Lewis, 1973), and asserting that the couple can work through their problems by offering the pair aid when problems arise (Julien, Markman, Leveille, Chartrand, & Begin, 1994; Milardo, 1983; Milardo & Lewis, 1985). In contrast, the interference model asserts that network members contribute to the breakdown of dyadic unions by fostering partners' feelings of dissatisfaction with their relationships. These models are hypothesized to function through the mechanisms of uncertainty reduction, social comparison, social sanctions, resocialization, and self-regulation. Although most research considers how these processes work in dating relationships (Bates, 1942; Parks & Adelman, 1983; Surra & Milardo, 1991; Sussman, 1953; Titus, 1980), there is reason to believe that the processes also operate in marriages. …