BACKGROUND The reported prevalence of ASDs in the United States as well as in other developed countries has increased dramatically in the last few years. This increase is likely the outcome of several factors: greater awareness of ASDs on the part of both parents and professionals, leading to earlier identification; changes in definitions related to ASDs (the wider use of the diagnostic category of Asperger's syndrome, for example); and perhaps an increase in environmental triggers of ASDs in genetically susceptible infants. At present, the best data on the prevalence of ASDs point to a rate of in 1 per 110 children, and a substantially higher rate in males. ASDs are defined behaviorally. There is no biological marker that points to a diagnosis of autism, and, as is well known in the medical field, the same symptoms can indicate various underlying conditions. About 10 percent of children diagnosed with ASDs have known medical conditions or disabilities such as Fragile X syndrome, but no such association has been identified in the other 90 percent of cases. The best current thinking is that there may be multiple genetic mutations contributing to susceptibility for ASDs. Although the pace of research into the causes of ASDs was very limited for many years, increased research funding to the National Institutes of Health, along with private funds, have substantially accelerated research opportunities. EARLY IDENTIFICATION AND EARLY INTERVENTION SERVICES A decrease in the age of identification of children at high risk for developing ASDs has occurred during the last few years as information about early warning signs or red flags for autism has been disseminated widely, and screening tools designed to identify ASDs in toddlers aged between 18 and 24 months have achieved wider use. Recent research appears to indicate that many children who are later diagnosed with autism can be identified by 12 months of age (Ozonoff, Losif, Baguio, Cook, Hill, Hutman et al., 2010). Researchers are also working on tools to identify infants aged between 12 and 15 months who are at high risk for developing ASDs. At present the mean age for diagnosis of ASDs is about 4 years, but that mean age is likely to decrease as a highly regarded evaluation tool, the Autism Diagnostic Observation Schedule (ASDOS), becomes available in a version designed for use with toddlers (publication is expected in 2012), and as other new diagnostic tools for use with toddlers at risk for ASDs gain broad acceptance. Because there is impressive evidence that early intervention is associated with better outcomes for infants and toddlers with ASDs (Bruder, 2010; Dawson, 2008), the importance of the development of such tools is clear. The Individuals with Disabilities Education Act (IDEA) Part C serves infants and toddlers with developmental delays from birth to age 3. Earlier identification of infants at high risk of developing ASDs and increased diagnostic evaluations of 2-year-olds at high risk should be accompanied by an expansion in the number of children receiving early intervention services. Such services are provided through each U.S. state, and there is great variation in the intensity of services delivered--some states provide such limited amounts of service time as to raise serious doubts about the effectiveness of those services. Moreover, with the budgetary strain that most states are currently experiencing, expansion of service intensity is very unlikely to occur in the foreseeable future, even though parents are already increasingly accessing private insurance and Medicaid waivers to help obtain adequate appropriate early intervention services for their children. When the topic of effectiveness of intervention arises, so too does a question about the availability of research-supported models for serving infants and young toddlers with ASDs. Until recently few such models existed. One of those models is the Early Start Denver Model for Young Children with Autism (Rogers & Dawson, 2010), a comprehensive model that incorporates behavioral principles within a developmental framework focused on social interaction, communication, and relationships. …