Investigated internal consistency reliability and criterion validity of the Asperger Syndrome Diagnostic Scale (ASDS) in a well-characterized sample of 120 children ([X-bar][subscript age] = 9.91; autism [AUT] n = 54; non-autism [NOT] n = 66) who completed comprehensive outpatient evaluations with a gold-standard measure, the Autism Diagnostic Observation Schedule-2. With the exception of a low Cognitive alpha in the AUT group, internal consistency reliabilities ranged from moderate to high. Significant between-group mean differences were observed for all scores. Receiver operating characteristic analyses indicated Area Under the Curve in the fair range (0.71). Cutoff points and interpretation are discussed. The ASDS appears most useful in cases of either low or high scores or as an adjuvant to gold-standard measures.