Autism is a complex neurodevelopmental disorder that forms part of a spectrum of related disorders referred to as Autism Spectrum Disorders (ASD). Like other complex neurodevelopmental disorders (e.g., schizophrenia), ASD is thought to be the final common pathway of multiple etiological (largely genetic) and neuropathological mechanisms. In the absence of a biological marker, ASD is defined behaviorally, its clinical presentation characterized by impairments in reciprocal social interaction and in communication with others, and by a preference for repetitive, stereotyped behaviors. Our understanding of autism has changed dramatically over the past decade. We now know that autism is not one disorder, but several closely related “disorders”, including Asperger syndrome, atypical autism, and disintegrative disorder. They may involve a range of behaviors at different ages and degrees of functioning, thus the term “autism spectrum disorder”. Along with these changes in classification, there has been a greater understanding of the causes of autism. Developmental delay, epilepsy, minor facial and bodily abnormalities, increased rate of obstetrical complications, an unequal sex ratio, and extremes of head size represent subtle, but still not clearly defined, signs that autism is a neuropsychiatric disorder. It appears that pharmacological interventions may have a limited role to play in the overall therapy of the autistic child. Medications may be most helpful in reducing hyperactivity, impulsivity, and aggressive and obsessive behaviors. For the development of everyday life skills, one-on-one behavioral therapy seems to be mandatory.