Portfolios, collections of student work representing a selection of performance, are being used in classrooms today in the tradition of the visual and performing arts in which they serve to showcase a student's best pieces and the student's evaluation of the strengths and weaknesses of the pieces. Portfolios are useful as a support to new instructional approaches that emphasize the student's role in constructing understanding and the teacher's role in promoting understanding. Although there is no single way to develop portfolio programs, in all such programs students are expected to collect, select, and reflect on their work. Research supports the finding that student awareness of work and of evaluation strategies is enhanced through portfolios. The use of portfolios is not without drawbacks, primarily in the time and effort required, but these are generally seen to be worthwhile burdens. A brief summary of research into portfolios highlights some current projects that investigate their use. Sources of information about portfolios are listed. (SLD)