This study reaffirms our previous work documenting a higher number of Emergency Department (ED) visits by adolescent females with Autism Spectrum Disorder (ASD) as compared to adolescent males with ASD, as well as significantly more ED visits by older adolescents than younger adolescents with ASD. Combined externalizing and internalizing psychiatric co-morbidities as well as internalizing conditions alone predict a higher number of ED visits in this study. Illness severity as demonstrated by patterns of visits to primary care physicians and psychiatric referrals prior to ED visits and the prescription of two or more classes of psychotropic medications also predict higher number of ED visits. Finally, as expected, previous ED visits predict future ED visits. The identification of these factors may prove helpful in determining adequacy of current supports and resources for teens with ASD navigating the challenges of adolescence.