The effects of task size on rate of responding and on-task behavior as well as on nontask-related behaviors of students with autism and mental retardation on a repetitive task under conditions of no reinforcement for responding was analyzed. Task size, defined as the presence of either 36 or 250 beads in a container at the onset of the session, was compared in an alternating treatment design. The small-task condition resulted in higher on-task behavior for all participants and in higher work rate for four of the five participants. For the four participants who engaged in inappropriate use of task materials, higher levels of this behavior occurred in the large-task conditions. Other nontask-related behaviors were higher in the large-task condition for all participants with the exception of stereotypy, which was higher in the small-task condition for one participant. Better work-related behavior occurred for these participants in small- than in large-task conditions even though no tangible reinforcement was provided for task responding. Implications of these results are discussed in the context of arranging workplace environments to maximize productivity of persons with developmental disabilities.