The 2006 Forbeck Forum focused on a question that has captured the attention of cancer scientists and cancer research funding bodies around the world. Does every cell in a tumor, whether liquid (leukemia) or solid, have equal ability to sustain cancer growth or are some cells within the tumor more potent than others? The answer to this question has the potential to alter research approaches away from study- ing the cellular and molecular proper- ties of entire tumor tissue towards focusing on the tumor-initiating cells or so called cancer stem cells (CSC). There was much discussion at the Forum on the best nomenclature for these cells. Evidence is emerging that for many tumors, they are organized as cellular hierarchies that are sustained by stem- like cells in much the same way as normal organs. To gain a clearer picture of CSC and their similarities and differences to normal stem cells, the 2006 Forum assembled 12 leading stem cell scientists whose interests ranged from stem cell biology of lower organisms like Drosophila to blood and intestinal stem cells of the mouse, to normal human hematopoietic stem cells (HSC) and leukemic stem cells (LSC). The unifying theme of the Forum was that progress to identify and characterize CSC from different tumors and to under- stand their importance in cancer will only come when we understand how normal stem cells for each organ actually work. One field of study, normal or neoplastic, informs the other. Indeed by understanding the genetic and epigenetic programs that govern normal stem cells, we can begin to understand how the neoplastic process subverts normal stem and progenitor cells. This Forum showed once again the value in bring- ing together investigators from different stem cell areas that often do not talk to each other and having them focus their attention on one question. New research directions were formulated, collaborative research projects were developed, and ultimately a strategy for progress in this promising field was stimulated in each of the participants.