In the present single case study the reactions of a severely mentally handicapped adult with autistic behaviour to simple instructions were investigated; in each case with and without gestural facilitation. This procedure was varied both with regard to persons and to situations. The correct following of requests as well as special behaviour such as uncertainty, smiling, delay of reactions and enthusiasm was registered and analysed by videotape. It could be clearly proved that the requests which were supported by gestures were more often performed correctly. On top of that it could be observed that under these circumstances the handicapped person was less uncertain, showed fewer stereotypies and was generally more interested. No influence could be noticed on the delay of reaction as well as on the person's enthusiasm. No difference could be seen between different persons and situations. Further research projects should particularly analyse how far the use of gestures does not only serve more communication but also has an influence on the range of behavioural disorders.