This study is a cluster randomized controlled trial of the Prevention and Relationship Enhancement Program (PREP; H. J. Markman, S. M. Stanley, & S. L. Blumberg, 2001). Fifty-seven religious organizations (ROs), consisting of 217 newlywed couples, were randomly assigned to 1 of 3 intervention conditions: PREP delivered by university clinicians (U-PREP), PREP delivered by RO clergy (ROPREP), and naturally occurring (NO) marriage preparation. Self-reported relationship satisfaction, negative behavior, and positive behavior were assessed at preintervention, postintervention, and 1-year follow-up. Trajectories of relationship satisfaction showed no change over time and did not differ across conditions. Trajectories of negative behavior for RO-PREP wives showed significantly greater linear declines in comparison with NO trajectories. Trajectories of positive behavior for NO and U-PREP partners showed significant declines compared with RO-PREP trajectories. Effectiveness, transportability, and dissemination of marital distress prevention programs in community settings are discussed.