This volume contains the proceedings of an International Sympo- sium on the Biology and Pharmacology of Tumor Cell Differentiation- held on June 29-July I, 1986 at the University of Tromso, Norway. The objective of this meeting was to bring together scientists from various disciplines to discuss recent advances in the understanding of tumor cell differentiation and to bridge the gap between experimental findings and clinical application of new knowledge. Thus the infor- mation will be of value not only to basic scientists involved in mol- ecular and cell biology, but also to pharmacologists and clinicians trying to develop the concept of tumor cell differentiation as a thera- peutic modality. Each plenary speaker and selected poster presenters were requested to submit a comprehensive, up-to-date review of recent contributions to their disciplines related to differentiation and: hematopoietic factors and leukemic cells in culture vitamin deriva- tives and polyamines; nucleosides and methylation; and cell interac- tions.