Adolescent ego-development trajectories were related to close-relationship outcomes in young adulthood. An adolescent sample completed annual measures of ego development from ages 14 through 17. The authors theoretically determined and empirically traced five ego-development trajectories reflecting stability or change. At age 25, the sample completed a close-relationship interview and consented for two peers to rate the participants’ego resiliency and hostility. Participants who followed the profound-arrest trajectory in adolescence reported more mundane sharing of experiences, more impulsive or egocentric conflict-resolution tactics, and less mature interpersonal understanding in their young adult relationships, and their young adult peers described these participants as more hostile. Participants who attained or maintained higher levels of ego development in adolescence reported more complex sharing of experiences, more collaborative conflict-resolution strategies, and greater interpersonal understanding, and their young adult peers rated them as less hostile and as more flexible.