This study is part of a programmatic line of research into the use of basic positive reinforcement procedures for improving working memory in children with autism spectrum disorders. The authors evaluated the effects of multiple exemplar training, utilizing positive reinforcement, on performance of a "digit span backwards" task--a test of working memory that entails sequential relational responding. All three participants showed improved performance on directly trained stimuli as well as maintenance and generalization to untrained stimuli. The results provide further support for the general hypothesis that performance on working memory tasks is amenable to improvement via behavioral intervention and has implications for treating such tasks as relational operants. Implications for future research and the development of clinical interventions are discussed. (Contains 2 figures.)