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Despite efforts to detect autism spectrum disorder during toddlerhood, many children with autism spectrum disorder remain undiagnosed until school age. To identify characteristics of children whose autism spectrum disorder might not be diagnosed during toddlerhood, this study used archived Autism Diagnostic Interview-Revised records to examine the historical presentation of autism spectrum disorder symptoms in 48 school-age children with autism spectrum disorder. Children diagnosed after starting school (Late-Diagnosed; n？=？24) were compared to age-matched children diagnosed before school age (Early-Diagnosed; n？=？24). Symptom presentation was similar between groups, with the Late-Diagnosed group exhibiting only marginally fewer symptoms historically. The most commonly reported historical symptoms were negative symptoms, namely, deficits in social behaviors. Positive symptoms, such as unusual preoccupations, rituals, and mannerisms, were less commonly reported. These findings may aid earlier identification of autism spectrum disorder in children who would likely be diagnosed at school age