In this study, using a national recruitment strategy, we tested the different factors that influence retention in four different types of relationship education (RE), a self-directed book, assessment and feedback, and a six session Couple CARE program delivered by email or by phone. Of all the factors considered, required program effort, highly valuing marriage, religiosity, education, and step-family status were able to predict with seventy percent accuracy which couples would complete or not complete their RE experience. Program effort was substantially better at predicting retention than all other variables. Retention was high in the book and assessment conditions but was much lower in the two Couple CARE conditions where more effort and time was required. Initial engagement was higher in the email based Couple CARE condition but overall retention was higher in the phone based condition. Important implications for current and future RE efforts are proposed.