Even though diffusion chamber culture was commenced long before ortho dox tissue culture by Metchnikoff (1887) there have been only sporadic attempts to use this methodology to study cell proliferation (review by Carsten, Chap. 1). Not so long ago diffusion chamber culture was nicknamed confusion chamber culture. I believe this conference has removed the confusion and will truly point out the intrinsic value of the system. It is not a substitute for established in vitro culture nor for in vivo studies. It complements both. Dr. Arne B~yum introduced diffusion chamber culture at Brookhaven National Laboratory. After some modest success in showing that one could culture human bone marrow and with appropriate stimuli induce erythro poiesis in diffusion chambers, several of the participants at this conference visited Brookhaven to learn firsthand this simple technology and to apply it in their own laboratories. However, the technique did not spread widely and controversy arose in which the same question was repeatedly asked: Can the diffusion chamber technique provide information that is not ob tainable more rapidly and easily, and at less expense by the in vitro tech niques? As a result of our deep interest in and involvement with diffusion chamber culture Dr. A. L. Carsten and I organized this conference. A major objective of this conference was to seek answers to the above question.