G A A b st ra ct s association of anxiety and gastrointestinal disorders in these children. Increased severity of anxiety symptoms is associated with the diagnosis of Asperger's and with higher IQ in children with ASD. Whether or not there is any relationship between anxiety and GI symptoms in children with ASD is not known Objectives: To characterize chronic GI symptoms in children with ASDs and their potential relationship with anxiety. Methods: The Autism Treatment Network Registry enrolled 3122 children ages 2 to 18 yr with an ASD diagnosis between September 2007 and July 2011 at 14 sites in the US and Canada. Autism Diagnostic Observation Schedules (ADOS) were administered to confirm an ASD diagnosis (Autism, PDD-NOS, or Asperger's). Among information collected upon entry, parents completed a GI symptom inventory, as well as Child Behavior Checklist (CBCL). GI symptom inventory identified type and prevalence of chronic GI symptoms. Anxiety Problems T-scores from the CBCLs were used to classify anxiety level as no anxiety (NA) (<65), borderline anxiety (BA) (65-70), or clinical anxiety (CA) (≥70). Scores from modules 1, 2, 3 and 4 of ADOS were used to place children in one of four verbal ability groups; non-verbal, some words, phrase speech, and verbal. The Stanford-Binet IQ test was used to characterize children with low IQ (<70) or high IQ (≥70). Results: One third (33%) of children were reported to have had at least one chronic GI symptom. Chronic GI complaints were greater in children with CA compared to those with NA (p<0.00005). Among ASD subtypes, chronic GI complaints were more likely in children with Asperger's than Autism (p=0.02) and in those with IQ ≥70 compared to IQ <70 (p=0.03.) Rates of GI complaints did not differ between the four verbal ability groups. Conclusion: Chronic GI symptoms occur in 1 out of 3 children with ASD. Further, Clinical Anxiety is associated with chronic GI symptoms in these children. As with rates of anxiety in previous studies of ASD study groups, increased rates of chronic GI symptoms were associated with diagnosis of Asperger's and higher IQ. Although verbal expression is known to be better in children with Asperger's than other ASD diagnoses as well as with higher compared to low IQs, the presence of chronic GI symptoms in our study group of children with Asperger's and high IQ is not due to increased verbal expression. Further studies are needed to investigate the relationship between anxiety and GI symptoms in children with ASD, and a potential causal relationship between anxiety and chronic GI symptoms in children with ASD.