It may seem strange at first sight that such a formal and routine procedure as constructing an index to psychoanalytic case material could be the focus of active, and at times exciting, research. However, this is indeed the case, and the present paper aims at giving some of the work which has been going on in the research committees of the Index.

Those of us who work on the Index have been impressed by the way in which the need to categorize and classify psychoanalytic material derived from the analyses of child patients forces us to think about our theoretical models, to go into these models in more detail, occasionally to supplement or modify them, and finally to define exactly what we mean by the terms we use. There is a constant interaction between our clinical material and our theoretical formulations, an interaction which seems to us to be an essential constituent of all scientific procedures (Sandler, 1961).