In this meta-analytic study, the authors examined the efficacy of marriage and relationship education (MRE) on 2 common outcomes: relationship quality and communication skills. A thorough search produced 86 codable reports that yielded 117 studies and more than 500 effect sizes. The effect sizes for relationship quality for experimental studies ranged from d = .30 to .36, while the communication skills effect sizes ranged from d = .43 to .45. Quasi-experimental studies generated smaller effect sizes, but these appeared to be due to pretest group differences. Moderate-dosage programs produced larger effect sizes than did low-dosage programs. For communication skills, published studies had larger effects than those of unpublished studies at follow-up; there were no publication differences for relationship quality. There was no evidence of a gender difference. Unfortunately, a lack of racial/ethnic and economic diversity in the samples prevented reliable conclusions about the effectiveness of MRE for disadvantaged couples, a crucial deficit in the body of research. In addition, intervention outcomes important to policy makers, such as relationship stability and aggression, rarely have been addressed. (Author abstract)