The study aims were to identify developmental trajectories of young children with autism and investigate their prognostic factors. The participants were 208 children, assessed first at the age of 5 years, followed longitudinally, and reassessed 3 years later. The children's clinical characteristics and the interventions received were recorded. The results indicated two distinct outcome groups with more stability than change. When changes did occur, they pertained to symptom severity (which decreased) and speech level and adaptive behavior (which improved). A logistic regression analysis pointed out two main risk factors (symptom severity and speech level) and two main protection factors (communication skills and person-related cognition). Surprisingly, the amount of intervention (in terms of number of hours) was not related to outcome.