Amphibian tissues seem to resist oncogenesis in proportion to their regenerative capacity, a phenomenon most easily seen in relation to limb regeneration. There is evidence that mammalian tissues also possess, in addition to and distinct from the capacity for physiological renewal, a limited and not always overtly evident degree of amphibian-like capacity for regeneration (epimorphic regeneration). It is the thesis of this paper that cancer in mammals would seldom occur were it not for a local destruction or exhaustion, secondary to injury or aging, of this normal amphibian-like regenerative capacity.