Accurate spelling is a complex act that requires cognitive and linguistic knowledge of the phonological, morphological, syntactical, and semantic principles of our language. Students with disabilities frequently exhibit spelling difficulties related to language learning disorders and inefficient cognitive processing. These difficulties often are developmental in nature. Remediation of spelling disorders in students with disabilities requires accurate, comprehensive assessment. Accurate, comprehensive assessment involves the use of both formal and informal assessment measures. In this article, we discuss the theory and research that support the assessment of spelling in students with disabilities and we describe formal and informal spelling assessment procedures. (Contains 1 table.)