The topic of early intervention for autism is widely researched and discussed within the literature. The application of applied behavioral analysis (ABA) continues to be an important topic. Due to the extensive amount of research on behavioral treatments for autism, and its widespread practice, the focus of this paper will be based upon treatment of autism using learning theory and behavioral principles. Specifically, the work of Lovaas will be reviewed followed by a brief examination of replication and follow-up studies. The efficacy of ABA style treatment programs will be reviewed along with methodological concerns that impact on the validity of treatment results.