Purpose: The purpose of this systematic review was to synthesize evidence from studies examining the effect of exercise interventions on stereotypic behaviours in children with autism spectrum disorder (ASD). Methods: Only exercise-related physical therapy (PT) interventions were included. A multifaceted search strategy identified studies published between 1980 and 2007. Quality was assessed using the American Academy of Cerebral Palsy and Developmental Medicine (AACPDM) Study Quality Scale, the Clinical Relevance Tool for Case Studies, and the Quality, Rigour or Evaluative Criteria tool. Results: Seven studies met our inclusion criteria; four of these used single-subject research designs, two were group studies, and one was a case study. Ages and behavioural characteristics of the children (N ¼ 25) varied among the studies. Levels of evidence ranged from II to V (of a possible I-V). Study quality scores ranged from 2 to 5 (range: 0 to 7); mean ¼ 3.9, mode ¼ 5. Few studies in this area of PT practice have been published, and those identified scored low levels of rigour on the AACPDM criteria. Conclusions: Research suggests that exercise provides short-term reductions of stereotypic behaviours in children with ASD. Future research with stronger evidence levels, greater rigour, and longer-term outcome assessment is required to determine specific exercise parameters.