This paper contains a description of the cross-over type of experimental design as well as a case study of its use in field testing audiovisual materials related to teaching handicapped children. Increased efficiency is an advantage of the cross-over design, while difficulty in selecting similar format audiovisual materials for field testing is a limitation. Types of research questions which can be answered by this type of design are discussed. A diagram of the cross-over technique and data tables from the case study are included. (STS)