Research has indicated children with autistic disorder often demonstrate below average intelligence. Others have suggested intelligence of the autistic population has been underestimated. A gap in the current literature reflects the need to examine the accuracy of assessment of intelligence of children with autistic disorder. The research questions underlying this study addressed tools professionals use to assess intelligence of children with autistic disorder, how tools are selected, the level of confidence in the accuracy of results, and what level of consensus exists among experts. This Delphi study used a panel of 20 autistic disorder experts and 3 rounds of surveys to establish expert consensus of practices for gaining an accurate measure of intelligence and to determine if an appropriate tool is available to measure intelligence of children with autistic disorder. This study was based on the Lockean inquiring systems philosophical perspective with a sequential, exploratory, mixed methods design and employed the constant comparative method for data analysis. Emergent themes included strategies used for assessing intelligence in this population, barriers to determining accurate results, and methods for mitigating the influence of barriers. With moderate to strong consensus among participants, the findings demonstrated lack of availability of an appropriate measure of intelligence for children with autistic disorder. This study has the potential to contribute to positive social change with findings justifying the development of an appropriate assessment tool which will enhance life opportunities of children with autistic disorder when more accurate measures lead to appropriate placement in academic, vocational, and social settings.