There is a growing body of evidence that individuals with autism spectrum disorder (ASD) frequently experience co-occurring psychiatric symptoms. This scientific panel integrates clinical and epidemiological perspectives to examine the conceptualization, measurement, and negative outcomes of this co-occurrence. Our first talk highlights key insights regarding the conceptualization of psychiatric syndromes in ASD derived from clinical evaluations of several thousand children and adolescents with ASD, other psychiatric syndromes and typical development. Talk 2 synthesizes the literature on comorbid psychopathology in ASD, examining how different measurement approaches may influence prevalence estimates. Using national data, talks 2 and 3 then examine the relationship of co-occurring psychiatric symptoms in ASD to life course outcomes, in particular adverse childhood experiences and criminality. The overarching goal of this panel will be to consider the implications of co-occurring psychiatric syndromes in ASD to epidemiologic research, clinical practice and public health – that is, to consider how our conceptualization of psychiatric co-occurrence may inform etiological models, measurement and treatment development as well as our ability to address the real-word service needs of individuals with ASD.