Although assessment is a critical component in the education and treatment of persons who have autism, there is insufficient information about the types of assessment instruments that are used routinely by practitioners. This brief report describes a survey of national service centers to determine their use of standardized instruments and the purposes of their assessment practices. Data from centers representing 30 states revealed that (a) the number of assessment instruments endorsed by centers increased as centers adopted a “multidisciplinary” approach to education and treatment, (b) the largest proportion of instruments fell within intellectual, motor, and language/communication domains, and (c) instruments were used most frequently for diagnostic and curriculum design purposes. Agreement among practitioners on the selection of instruments occurred most frequently in the domains of projective, adaptive behavior, and family assessment. The implications from these findings for assessment practices in autism are discussed.