Single-case design (SCD) research focuses on finding powerful effects, but the influence of this methodology on the evidence-based practice (EBP) movement is questionable. Meta-analytic procedures may help facilitate the role of SCD research in the EBP movement, but meta-analyses of SCDs are controversial. The current article provides an introduction to the special issue on meta-analyses of SCD research by discussing concerns regarding the internal and external validity of these designs. Specific considerations for increasing the validity of SCD meta-analyses are provided, as are brief overviews of the articles included in the special issue.