This study aimed to investigate the number of exclusion trials necessary for teaching auditory-visual relationships to individuals with autism and Down syndrome. Study participants were seven individuals with autism and a history of early behavioral intervention (EI), four adults with autism without a history of early behavioral intervention (NI), and three adults with Down syndrome. A set of procedures was used for teaching the auditory-visual matching to sample, and naming responses of the new stimuli were tested. For the individuals with autism and EI and for the individuals with Down syndrome, the required number of repetitions was stable and concentrated in the minimum programmed by the procedure (two repetitions). However, the procedure was not effective for teaching new conditional relationships for the adults with autism and NI. The results indicate that the procedure can constitute an important teaching technology; however, its efficacy appears to vary depending on the educational profile of the participant.