Autism spectrum disorders (ASDs) are neurodevelopmental disorders whose prevalence has risen over the past two decades. Current drug treatments for ASDs and the related disorders--fragile X syndrome (FXS) and Rett syndrome--target specific symptoms but do not address the basic underlying etiologies. However, based partly on an improved understanding of the neurochemical underpinnings of FXS, pharmacotherapy for this syndrome has progressed to the point of clinical trials of several novel drug treatments. By contrast, our overall understanding of the neuropathophysiology of ASDs is still rudimentary. There is hope in the field that knowledge and experience gained in the study of fragile X and Rett syndromes may be applicable to the larger autism patient population. In this review, we discuss how recent advances in our understanding of the biochemistry and neuropathology of these disorders could lead to new more effective treatments for ASDs.