There is an urgent need for increased knowledge about all aspects of autism spectrum disorder (ASD), from identifying risk factors, to understanding underlying biology, to developing new more effective treatments, to bringing evidence based practices into the community. Over the past decade, research addressing these issues has expanded dramatically due to greater availability of resources and wider appreciation of the individual, family, and societal costs of ASD. To comprehend the current state of ASD research and begin to plan next steps, Congress requested an annual update of scientific advances. This book is a summary on the advances in autism spectrum disorder research that has been ongoing from calendar years 2007 through 2011.