The purpose of this meta-analysis was to determine the extent of the overall relationship between previously tested variables and sight-reading. An exhaustive survey of the available research literature was conducted resulting in 92 research studies that reported correlations between sight-reading and another variable. Variables ("n" = 597) were grouped by construct (e.g., music aptitude, technical ability) and separate meta-analyses were conducted for each construct. Construct had a variable effect on sight-reading, with improvisational skills, ear-training ability, technical ability, and music knowledge correlating most closely with sight-reading, while attitude and personality were unrelated to sight-reading. Additionally, the study examined differences in effect size by type of publication (published study, unpublished thesis), the experience level of the sight-reader (elementary, secondary, college nonmusician, college musician), sight-reading mode (instrumental sight-reading, sight-singing), and type of sight-reading test. The few differences suggest future investigation of a developmental component to sight-reading is warranted. In general, music constructs that improve with practice correlated more strongly with sight-reading than did stable characteristics. These results support sight-reading being considered a music skill that improves with the musicality of the performer rather than a simple visuo-motor decoding process.