For three decades after Leo Kanner's first clinical description, research progress in understanding and treating autism was minimal but since the late 1960s the growth of autism discoveries has been exponential, with a remarkable number of new findings published over the past two decades, in particular. These advances were made possible first by the discovery and dissemination of early intensive behavioural intervention (EIBI) for young children with autism that created the impetus for earlier accurate diagnosis. Other factors influencing the rapid growth in autism research were the first accepted diagnostic test for autism, the Autism Diagnostic Interview and Observation Schedule (ADI and ADOS). Developments in brain imaging and genetic technology combined to create a fuller understanding of the heterogeneity of autism, its multiple aetiologies, very early onset and course, and strategies for treatment. For a significant proportion of children with autism, it appears EIBI may be capable of promoting brain connectivity in specific cerebral areas, which is one of autism's underlying challenges. Disagreements about the most appropriate early intervention approach between developmental and behavioural psychologists have been unproductive and not contributed to advancing the field. Naturalistic behavioural and structured discrete trial methods are being integrated with developmental strategies with promising outcomes. Over these past 30 years, young people with autism have gone from receiving essentially no proactive treatment, resulting in lives languishing in institutions, to today, when half of children receiving EIBI treatment subsequently participate in regular classrooms alongside their peers. The future has entirely changed for young people with autism. Autism has become an eminently treatable condition. The time is overdue to set aside philosophical quarrels regarding theories of child development and apply what we know for the benefit of children with autism and their families.