To compare gastrointestinal (GI) problems among children with: (1) autism spectrum disorder (ASD), (2) developmental delay (DD) and (3) typical development (TD), GI symptom frequencies were obtained for 960 children from the CHildhood Autism Risks from Genetics and Environment (CHARGE) study. We also examined scores on five Aberrant Behavior Checklist (ABC) subscales comparing ASD children with high versus low frequency GI symptoms. Compared to TD children, those with ASD [aOR 7.92 (4.89-12.85)] and DD [aOR 4.55 (2.51-8.24)] were more likely to have at least one frequent GI symptom. Restricting to ASD children, those with frequent abdominal pain, gaseousness, diarrhea, constipation or pain on stooling scored worse on irritability, social withdrawal, stereotypy, and hyperactivity compared with children having no frequent GI symptoms. Frequent GI problems affect young children with ASD and DD more commonly than those with TD. Maladaptive behaviors correlate with GI problems, suggesting these comorbidities require attention.