Three functional assessments were conducted with a client with self-injurious behavior (SIB), which indicated that SIB appeared to be sensitive to attention as reinforcement. In addition, levels of SIB were much higher when the client was seated in his wheelchair An additional analysis was conducted in which client location (in and out of wheelchair) was altered while reinforcement contingencies (attention) for SIB were held constant Levels of SIB again were higher when the client was positioned in his wheelchair; even though the consequences for SIB were identical. The results of this final analysis suggested that the wheelchair functioned as an establishing stimulus altering the efficacy of social positive reinforcement. (C) 1997 Elsevier Science Ltd.