The Gilliam Autism Rating Scale-Second Edition (GARS-2) is a screening tool for autism spectrum disorders for individuals between the ages of 3 and 22. It was designed to help differentiate those with autism from those with severe behavioral disorders as well as from those who are typically developing. It is a norm-referenced instrument that reflects the conceptualizations of autism per the "Diagnostic and Statistical Manual of Mental Disorders" (fourth edition, text revision; American Psychiatric Association, 2000) and the Autism Society of America (1994). The GARS-2 was designed to be a supplementary tool for the diagnosis of autism, and it is intended to be used with a variety of diagnostic tools and relevant information in comprehensive assessment protocols for autism. Furthermore, it is intended to facilitate data-driven approaches to assessment and intervention by incorporating a resource that links instructional objectives to assessment findings. This article describes the administration, scoring, and interpretation of GARS-2. It also presents the test's technical adequacy as well as some commentary and recommendations for it.