Adult attachment has been studied as an important predictor of romantic relationship quality in many empirical studies. This meta-analysis quantitatively summarized the associations between the two insecure adult attachment dimensions, anxiety and avoidance, and cognitive, emotional, and behavioral indicators of romantic relationship quality based on 73 previous studies with 118 independent samples of 21 602 individuals. More importantly, we examined the different effects of anxiety and avoidance on relationship quality. We also tested the potential moderating effects of gender on the strength of these associations. Meta-analytic results confirmed that both anxiety and avoidance were detrimental to the cognitive, emotional, and behavioral aspects of relationship quality. Compared with anxiety, avoidance was more negatively associated with general satisfaction, connectedness, and general support in relationships. In contrast, anxiety was more positively associated with general conflict in relationships. The moderating effect of gender was weak. However, supplementary analyses found that the type of couple interaction measures (self-report versus observation) significantly moderated the relations between insecure attachments and the behavioral indicators of relationship quality. Our results integrate and extend previous findings about the dynamics of adult attachment and romantic relationship quality. Copyright © 2012 John Wiley & Sons, Ltd.