The purpose of this study was to investigate the effectiveness of alternative communication training on the learning of shopping skills for elementary school children with moderate to severe mental retardation. The subjects are three elementary school children with moderate to severe mental retardation. The single subject research across subjects with multiple probe design was used. The independent variable was alternative communication training and the dependent variable was shopping skills. Data were collected on the three subjects during baseline, intervention, maintenance, and generalization phases. Visual analysis was used to analyze the effectiveness of the training. The observational analysis and social validity analysis using interviews with related individuals were also supplemented.Results of this study are summarized as followings:1. The alternative communication training is effective on the acquisition of shopping skills for the elementary school children with moderate to severe mental retardation. It is also effective in maintaining the results of such behavior change and in the generalization of the success.2. In addition to improved shopping skills, the subjects have also learned other skills during the period of this study.3. Interviews with related individuals have indicated that this research has a high social validity.