Each year the IACC releases its annual list of scientific advances that represent significant progress in the field. The twenty studies selected have given new insight into the complex causes of autism and potential risk factors, studied clues that could lead to earlier diagnosis, and evaluated promising early intervention strategies. The advances also address the prevalence of ASD both in the U.S. and internationally, as well as the service needs of people with ASD across the lifespan. The 2011 Summary of Advances provides short, plain language synopses of the top research breakthroughs selected by the committee from a pool of peer-reviewed articles nominated by the members. Articles are grouped according to the questions of the IACC Strategic Plan for ASD Research. Citations for the articles selected for the Summary of Advances, as well as a complete listing of those nominated, are included at the end of the document. A full listing of articles cited is included in the summary.