Teaching Portfolios are now common in higher education. They are used both developmentally and summatively in spite of the fact that many academics find them generically quite unfamiliar. This paper explores, primarily conceptually, the experience of one institution as to the ways in which portfolios have functioned in its processes and its practice. The paper introduces a small empirical sample of portfolios in an attempt to give concrete meaning to some of the points made. Ultimately, it questions whether portfolios can have a mixed developmental/summative mode of existence and still meet the purposes the institution intends. This raises the issue of the extent to which a summative mechanism can become an end in itself and can actively limit progressive potential.