We examined the effects of the Picture Exchange Communication System (PECS; Frost & Bondy, 2002) on the manding (requesting) and speech development of school-aged children with autism. In study 1, two participants, Damian and Bob, were taught PECS within a delayed multiple baseline design. Both participants demonstrated increased levels of manding after implementation of PECS. Only Damian demonstrated any measurable speech during study 1. His speech development occurred primarily during phase IV of PECS. Because of the positive relationship between Phase IV and increased speech for Damian, study 2 was conducted to confirm a functional relationship between phase TV procedures and speech development for an additional participant. Carl received phase IV training procedures in two conditions, administered in an ABAB design. In condition A, no reinforcement was provided for vocalization; in condition B, reinforcement was provided for vocalization after a delay of 3- to 5-s. The vocal reinforcement procedures in phase B differentially increased Carl's speech. Results are discussed in terms of research on augmentative and alternative communication and speech development for children with autism.