Passion and sexual satisfaction typically diminish in longer-term relationships, but this decline is not inevitable. We identified the attitudes and behaviors that most strongly differentiated sexually satisfied from dissatisfied men and women who had been together for at least three years (N = 38,747). Data were collected in 2006 from cohabiting and married men (M) and women (W) via an online survey on a major national U.S. news Web site. The vast majority of these participants reported being satisfied with their sex lives during their first six months together (83% W; 83% M). Satisfaction with their current sex lives was more variable, with approximately half of participants reporting overall satisfaction (55% W; 43% M) and the rest feeling neutral (18% W; 16% M) or dissatisfied (27% W; 41% M). More than one in three respondents (38% W; 32% M) claimed their sex lives were as passionate now as in the beginning. Sexual satisfaction and maintenance of passion were higher among people who had sex most frequently, received more oral sex, had more consistent orgasms, and incorporated more variety of sexual acts, mood setting, and sexual communication. We discuss implications of these findings for research and for helping people revitalize their sex lives.