Bone marrow is the point of origin of several cell types, including stromal cells. Adherent bone marrow stromal cells can differentiate into chondrocytes, adipocytes and osteoblasts. Several substances which modulate the dynamics and differentiation of bone marrow stromal cells have been identified. Recently it has been discovered that those bone marrow cells which are non-adherent in tissue culture for 3 days have osteogenic potential comparable to that of whole bone marrow cells. In the future, implantation of non-adherent bone marrow stromal cells may be of use as an aid in bone fracture healing, similar to whole marrow or adherent stromal cell grafting at present.