The purpose of this study was to test the hypothesis that word reading accuracy, not oral language, is associated with spelling performance in school-age children. We compared fourth grade spelling accuracy in children with specific language impairment (SLI), dyslexia or both (SLI/dyslexia) to their typically developing grade-matched peers. Results of the study revealed that children with SLI performed similarly to their typically developing peers on a single-word spelling task. Alternatively, those with dyslexia and SLI/dyslexia evidenced poor spelling accuracy. Errors made by both those with dyslexia and SLI/dyslexia were characterized by numerous phonologic, orthographic and semantic errors. Cumulative results support the hypothesis that word reading accuracy, not oral language, is associated with spelling performance in typically developing school-age children and their peers with SLI and dyslexia. Findings are provided as further support for the notion that SLI and dyslexia are distinct, yet co-morbid, developmental disorders.