ABSTRACT: This paper looks at the effects of aging on the response of skeletal muscle to exercise from the perspective of the behavior of muscle precursor cells (widely termed satellite cells or myoblasts) and regeneration. The paper starts by outlining the ways in which skeletal muscle can respond to damage resulting from exercise or other trauma. The age-related changes within skeletal muscle tissue and the host environment that may affect the proliferation and fusion of myoblasts in response to injury in old animals are explored. Finally, in vivo and in vitro data concerning the wide range of signaling molecules that stimulate satellite cells and other aspects of regeneration are discussed with respect to aging. Emphasis is placed on the important role of the host environment, inflammatory cells, growth factors and their receptors (particularly for FGF-2), and the extracellular matrix.