The effects of a parent-implemented naturalistic intervention on the communication skills of a 4-year-old boy with autism using an alternative and augmentative communication (AAC) system were investigated. The child's mother was taught to use 4 naturalistic teaching strategies that incorporated a picture communication system during 2 typical home routines. Generalisation probes to assess the caregiver's use of the intervention techniques and generalisation of the child's communication outcomes were conducted in 2 similar interactions. A multiple baseline design was used to evaluate the effects of the intervention. Data indicated an increase in the use of 2 caregiver-teaching strategies across two routines following treatment. No consistent changes were observed in the use of the other caregiver strategies across the routines. An increase in the child's frequency of initiations and responses and the use of the communication system also were observed. (Contains 3 tables and 11 figures.)