This volume is designed to provide a comprehensive overview of autism for the many educated and thoughtful parents, professionals, and other concerned citizens with an interest in these important issues. It has grown out of our assumption that there are many people interested in our field who want the most up-to-date information available without having to locate and read through the growing literature in this area. From our university bases, we are fortunate in having access to state-of-the-art information about autism and related developmental disorders. Our goal in this volume is to synthesize this information and present it comprehensively and objectively. This volume is the culmination of 2 years of hard work identifying, organizing, writing, rewriting, and editing the most up-to-date information available about people with autism, their families, and the state-of-the-art about the nature, causes, underlying mechanisms, diagnosis, and treatment of autism. We hope it will help the many friends, colleagues, families, and interested citizens who have expressed their interest in a publication of this kind. v Acknowledgments A project ofthis scope could not have been completed without the help of many fine friends and colleagues, too numerous to name. As with all of our professional activities we are indebted to our TEACCH colleagues and the many families and professionals we know in North Carolina, around the United States, and throughout the world for their interest, support, insights, and generosity in sharing their ideas and observations. We hope that our final product reflects their many superb contributions.