This study investigated the communicative behavior of five high-level and five low-level autistic children (ages 3-5 years). Differential responses of parents and a clinician to the children's protesting, responses, and initiations were assessed. Findings indicate differential interaction behavior and behavior problems of autistic children with their parents and a clinician. Both groups of autistic children reacted quite sensitively to different interaction partners and their communicative feedback. Low-level autistic children mainly used nonverbal protests when interacting with their parents. Parents tended to respond to appropriate communicative acts with new demands, while the clinician acknowledged the communication. Reassessment of the low-level group after 20 months of daily therapy showed a significant reduction of protests and noncompliance and an increase in parents' positive feedback. (JDD)