The present study investigated differences among children with three different patterns of autism symptom onset: regression, plateau, and no loss and no plateau. Cross-sectional data were collected from parents of children aged 3–17 years with an autism spectrum disorder (n = 2,720) who were recruited through a US-based online research database. Parental report of developmental characteristics was assessed through a parent questionnaire, and current autism symptoms were measured via the Social Responsiveness Scale and Social Communication Questionnaire. Multivariate analyses indicated that children with regression had a distinct developmental pattern marked by less delayed early development. However, following regression, these children evinced elevated autism symptom scores and an increased risk for poorer outcomes when compared with the other onset groups.