The category of autism has undergone huge changes over the past 20 years. This study was undertaken to analyze the changes and how parents have experienced the diagnostic process in France. Data were obtained from in-depth interviews with parents and psychiatrists, and from 248 questionnaires with open-ended questions filled in by parents. We compared the experiences of parents with adult autistic children to those of parents with young autistic children. Progressively earlier age at diagnosis was evidenced. These changes occurred later than in North America and the UK, due to the reluctance of French professionals to adopt the new classifications of diseases which they viewed as undervaluing both the physician's holistic clinical skills, and psychoanalytical interpretations. Parents' experiences and interviews with psychiatrists were analyzed in order to document changes over time in the diagnostic process following tensions between parents and professionals, and intra-professional debates in psychiatry. Our data support the notion that the diagnosis of autism is historically and nationally contingent. The interactions between changes in the diagnostic process, policy, and parental experiences have led to changes in the way autism is defined, understood, and experienced.