The purpose of this study was to compare the effects of simultaneous prompting instruction with high and low treatment integrity on the learning of children with developmental disabilities. Low treatment integrity was defined as not delivering a controlling prompt during 30% of the teaching trials. Three preschool children with autism and intellectual disabilities were taught to identify objects and professions in the study. An adapted alternating treatments design was used to compare the effectiveness and efficiency of simultaneous prompting instruction conducted with high versus low treatment integrity. The results showed that both conditions were effective in promoting learning. However, consistent data were not obtained for efficiency measures across children. The results, implications, and future research are discussed.