This article adopts a meta-analytic research framework to examine the strength of the relationship between working memory and simultaneous interpreting. This quantitative analysis utilizes a random effects model to combine multiple studies in an examination of differences between professional interpreters and various comparison groups as well as the relationship between working memory capacity and interpreter performance. Moderating and control variables are discussed, and a classification scheme for work on these topics is proposed. Two moderating variables are examined by testing the difference between working memory tests relying on auditory and visual stimuli as well as storage tasks (short-term memory) and processing tasks (working memory). Published studies were collected from several field-specific databases by querying working memory and simultaneous interpreting as key terms, and then supplemented by reviewing references, searching Google Scholar, and reviewing the work of scholars known to work in the area. Results are indicative of differences between professional and comparison groups, with professional interpreters exhibiting greater working memory capacity. Additionally, an overall positive correlation was observed between working memory capacity and measures of the quality of simultaneous interpreting.