This book represents a comprehensive endeavor to examine the multiple hypotheses that have been proposed to explain the cause of autism. Some confusion has arisen in defining exactly what are the specific criteria to be applied in diagnosing this disorder, to distinguish it from other neuropathologic conditions. In recent years, the issue of autism has reached major levels of concern and attention among scientific and general audiences. The authors have striven to make this book suitable for both the professional and the lay reader. Although much research effort and substantial funding amounts have been devoted to uncovering the cause of autism, little is currently known with certainty. Much like other unsolved medical mysteries, autism is believed to result from an environmental trigger interacting with a genetic propensity. As a result of the public alarm that has justifiably developed, numerous hypotheses have been generated without sufficient research evidence to identify the main pathologic process(es) causing autism. No one explanation has sufficient supporting data to claim a clear, comprehensive cause-and-effect relationship. Unfortunately, quite a few of these unverified proposals have persisted for various reasons. Some of these proposals, such as a purported link with vaccination, are still believed to be valid by the general public, in spite of numerous studies negating or refuting them. A major source of this confusion has resulted from the tendency of the popular press to overemphasize the meaning of "breakthrough" scientific discoveries, many of which are repetitions of previously discarded or discredited claims. The public is often uncertain and ill-informed about what issues are well-founded and deserve additional attention and credible support. Hence, the primary goal of this book is to separate fact from fiction for ultimately elucidating the true etiology(ies) of autism. In this process, unsubstantiated therapies will be questioned.