Within the field of autism spectrum disorder, the attribute "scientifically proven' it moil commonly urn in reference to the results of early behavioral treatment, and in particular, one style of early behavioral treatment. In this brief article, such claims are evaluated. Concerns raised by other researchers about the methodology of the original Lovaas (1987) study are briefly summarized. A particular concern that has been raised repeatedly u the loch of random assignment of participants to treatment versus control group. A more recent study (Smith, Groen, & Wynn, ZOOO), which included the necessary random assignment of participants to treatment versus control group and assessed multiple outcome measures, is reviewed. The results of the Smith et al. (ZOOO) study with random assignment appear to be less dramatic than the results from the original Lovaas (1987) study.