The purpose of this experiment was to assess whether manipulation of variables related to motivation and attention in children with autism would influence performance on standardized tests. Two different testing conditions were compared: One consisted of the usual standardized testing procedures; during the other, specific variables that were hypothesized to relate to each child's responsiveness to task stimuli were manipulated. Data were collected in the context of a repeated reversals experimental design with condition order varied within and across children. Six children participated in a total of 44 separate testing sessions, controlled for order of conditions, number of sessions, and type of test. Results showed consistent differences between the two conditions, suggesting that improving motivation and attention in children with autism may considerably influence test performance and interpretation. Findings are discussed in relation to the difficulty in administering and interpreting changes in performance on standardized tests with this population.