Rett syndrome is a congenital neurological syndrome, which in the classic phenotype only affects girls. The symptoms include lack of speech, stereotypic movements of hands, Dyspraxia and mental retardation, and these symptoms lead to communicative impairments. The purpose of this study was to examine whether the intervention method Intensive Imitation affected interaction/communication and initiative in a girl with Rett syndrome. The design of the study was a Single Subject Experimental Design with a three-week long intervention period where the girl participated daily in 30- minute sessions of Intensive Imitation together with the test conductor. Interaction, communication and initiatives were observed and analyzed before (Baseline A), during and after (Baseline B) the intervention period.