This article synthesizes the experimental literature that compares the academic, cognitive, and behavioral performance of adults with reading disabilities to those of average-achieving adult readers. The central question posed by this review is to what extent and in what manner do adults with reading disabilities differ from adults without reading disabilities on measures assumed to relate to overall reading competence. In all, 52 studies met criteria for a meta-analysis, yielding 776 effect sizes (ESs) with an overall a weighted ES of 0.72 (SD = 0.54). Moderate to high ESs in favor of adults without reading disabilities emerged on measures of cognition (naming speed [M = 0.96], phonological processing [M = 0..87], verbal memory [M = 0.62]) and achievement (word attack [M = 1.33], math [M = 0.75], vocabulary [M = 0.71], spelling [M = 1.57], and writing [M = 0.72]). Hierarchical linear modeling indicated that verbal IQ, vocabulary, math, spelling, and specific cognitive process measures (naming speed, phonological processing, and verbal memory) significantly moderated overall group ES differences. Significantly larger ESs emerged for studies with relatively higher IQ scores when compared to studies with IQ and reading scores in the same low range. Overall, the results support the notion that reading achievement and cognitive deficits in adults with reading disabilities are persistent across age. (Contains 3 notes and 5 tables.)