Multiple sleep problems have been reported in children with Autism Spectrum Disorder (ASD). The association of poor sleep with problematic daytime behaviors has been shown in small studies of younger children. We assessed the relationship between sleep and behavior in 1784 children, ages 2-18, with confirmed diagnosis of ASD participating in the Autism Treatment Network. Sleep problems were identified using the Children's Sleep Habits Questionnaire (CSHQ). The Parental Concerns Questionnaire (PCQ) was used to evaluate behavioral concerns and to define good or poor sleepers. Poor sleepers had a higher percentage of behavioral problems on all PCQ scales than good sleepers. Over three-fourths had problems with attention span and social interactions. Further delineation of this phenotype will help guide future interventions. (Contains 4 tables.)