During a symposium on the psychotherapy of the psychoses held under the auspices of this Section,† I took occasion to point out that, owing to the nature of their case material, many psychoanalysts had been forced to undertake this branch of treatment, whether they liked it or not. In the case of psychiatric classification the position is somewhat different. However much the psychoanalyst may choose to procrastinate, he cannot postpone indefinitely the task of correlating psychiatric data with his own systematic formulations on mental development. The more precise and dogmatic these formulations become, the more incumbent it is on the psycho-analyst to test them in the psychiatric field. Already some ventures have been made in this direction, notably in the work of Rickman,† Schilder,§ Stärcke‖ and others. The main justification for a renewal of these attempts lies in the fact that during the past four or five years, appreciable advances have been made in the psycho-analytic understanding of early stages of ego development. A great deal has been achieved by the analysis of small children, largely under the inspired stimulus of Melanie Klein, and already this work has produced reverberations in other directions. I am constrained to make this preliminary explanation in the hope of mitigating an impression which I fear still prevails in some quarters, namely, that in its relations to psychiatry, psycho-analysis displays the dogmatic over-compensation of an ignorant and none-too-welcome parvenu. Indeed, I should like to take this opportunity of stating that psycho-analysis, if even on the barest grounds of economy of effort, looks forward to an increasingly close alliance with pure psychiatry. And I hope to be able to indicate in this paper some problems on which the co-operating energies of the two sciences might well be concentrated.