OBJECTIVES:: The significance of the association between many gastrointestinal (GI) pathologies and autism has yet to be discovered. The aim of the present study was to review available evidence documenting any link between autism and GI histopathology in children. MATERIALS AND METHODS:: In a systematic review, the following sources were searched: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1980-August week 2, 2009), EMBASE (1980-August week 2, 2009), PubMed (last 180 days), Web of Science, and Scopus, using the terms "autism" or "autistic spectrum disorder" and "intestinal" or "gastrointestinal" or "colitis." In addition, relevant studies were identified through browsing the reference lists of the included articles for relevant citations. All children younger than 18 years old with autistic spectrum disorder who were examined for abnormal GI histopathology were included. Cohort studies published in the English language, reporting GI histopathological examination findings in children with autism, were included. Two independent authors performed data extraction. The methodological quality of each trial was assessed. RESULTS:: Eight studies have reported the histopathological features of the GI tract in children with autism and fulfilled inclusion criteria. In general, none of these trials appeared to be of high quality. Apart from intestinal lymphonodular hyperplasia, the majority of these findings were not consistent. CONCLUSIONS:: GI pathological findings in children with autism have been inconsistent. The present available evidence does not support or refute a link between GI histopathology and autism in children. The significance of intestinal lymphonodular hyperplasia in these children is unknown. Large properly designed prospective controlled trials addressing this issue are required.