Although the exact prevalence is not determined, a noticeable subset of individuals who enroll in adult education and training programs have either diagnosed or undiagnosed specific learning disabilities (SLD). Understanding SLD is important basic information for adult educators to inform program policies as well as determine effective instructional practices. This article discusses the development of definitions of SLD and current agreement on the nature of SLD relevant to working with adults. It concludes with implications for adult education programs. (Contains 1 figure.)