This meta-analysis is designed to build on the existing knowledge base by examining vocabulary interventions specifically for factors associated with child outcomes for at-risk children. Specifically, the authors addressed the following questions: (1) To what extent are vocabulary interventions an effective method for at-risk children prior to conventional reading instruction?; (2) What factors (e.g., pedagogical, methodological, intervention, or design) are associated with significant word learning gains for children at-risk?; (3) (How) are various risk populations (e.g., SES, ELL, low academic achievement, low vocabulary pretest scores) differentially affected?; and (4) How do cumulative risk factors affect children's vocabulary gains? The authors' results provide strong evidence for the overall effectiveness of vocabulary interventions for young, at-risk children. The effect sizes obtained are considered both educationally significant (Lipsey & Wilson,1993) and large (Cohen, 1988). Due to the inclusion of 14 unpublished studies (36% of the sample) with significantly lower effect sizes, it is possible that their overall effect size is a low estimate. The authors' results indicate that even more powerful interventions than have generally been conducted are needed for at-risk children and that the mechanisms through which to achieve this are related to the type of intervener, the explicitness of instruction, and whether specific words are targeted prior to the intervention. Altogether, their meta-analysis provides some promising recommendations for classroom settings for at-risk children. However, these moderator analyses should not be interpreted as testing causal relationships (Cooper, 1998; Viechtbauer, 2007). Rather, their results should be verified through experimental manipulations that vary these factors systematically. (Contains 5 figures and 6 tables.)