This paper addresses some of the important aspects of stem cell commitment to the bone cell lineage examining the various types of precursor cells, their responses to cytokines and other extracellular influences, and recent observations on the biochemical and molecular control of lineage-specific gene expression. The process of osteopoiesis involves the proliferation and maturation of primitive precursor cells into functional osteoblasts. The bone cells purportedly originate from mesenchymal stem cells that commit to the osteogenic cell lineage becoming osteoprogenitor cells, preosteoblasts, osteoblasts, and osteocytes. Further understanding of this developmental process requires that lineage-specific markers be identified for the various populations of bone cells and their precursors, that cell separation techniques be established so that cells of the osteogenic lineage can be purified at different stages of differentiation, and that these isolated cells are studied under serum-free, chemically defined conditions.