The Center for Disease Control estimates that one in 88 births result in a diagnosis of autism (CDC, 2012). Of those individuals diagnosed with autism approximately 25-61% fail to develop vocal output capabilities (Weitxz, Dexter, & Moore, 1997). The use of Augmentative and Alternative Communication (AAC) systems, such as Picture Exchange (PE) and Voice Output Communication Aids (VOCA) has been demonstrated as effective for those individuals to acquire a mand repertoire (Mirenda, 2003). The focus of the current study was to compare mand acquisition using PE and the iPad as a VOCA, in terms of acquisition rate and participant device preference, and with regard to collateral effects on vocalizations and disruptive behaviors. Additionally, the study evaluated the effectiveness of a teaching strategy using constant time delay with full-physical prompts (Sigafoos, Doss, & Reichel, 1989) in the acquisition of a mand repertoire using PE and the iPad as a VOCA, in five preschool aged children with autism. Finally, the devices were assessed in terms of their social validity. Three participants acquired the ability to communicate using the iPad as a VOCA more readily and two participants acquired the ability to communicate more quickly using PE, while the overall rate of independent manding was higher for four participants using the VOCA. The results of the study also indicate that the use of a constant time delay procedure with full-physical prompts was effective in the acquisition of both PE and the VOCA device. Regarding preference, four participants demonstrated a clear preference for the VOCA device and one for PE, when presented with the option to respond with either device. With respect to collateral effects, the data were largely inconclusive. For one participant there was an overall increase in vocalizations, for one participant there was an overall decrease in vocalizations, for the remaining three there was no systematic change in their rate of vocalizations during or following communication training. Regarding disruptive behaviors, an overall decrease in the occurrence was seen for two participants, for the remaining three the rates of occurrence did not change systematically following communication training. Finally, in terms of social validity, both the VOCA device and PE were found to be acceptable communication tools, with educators reporting that they would not only include such training within their classroom routines, but would also recommend its use in the future. / Educational Psychology