When properly implemented, prototype testing appears to provide one of the most direct and economical methods for identifying means to optimize the effectiveness of a product, and ultimately to validate a product's effect. The nine papers in this volume exemplify several categories of protytype testing conducted at different stages of the development process, under different conditions, and yielding different types of results. The first two working papers describe the use of status testing in selecting and sequencing outcomes and related content for spelling and composition skills instruction. The third paper describes an experimental investigation of the effect of two manipulated variables--tracing prompts and descrimination training--on kindergarten handwriting performance. At this stage of development, prototype testing can aid in important decisions about product specifications and in avoiding costly modifications later in development. As explained in papers four and five, using prototype testing in composition skills and drama, pupil performance data are of secondary interest at such early stages in development. The sixth paper suggests certain procedures for reporting classroom observation of a program lesson and illustrates these procedures with respect to programs in composition and drama. (RC)