Anuran and urodele amphibians develop spontaneous neoplasms in all major organ systems with the integumentary system a frequent target. Anurans and urodeles have spontaneous viral-associated tumors, the biological behavior of which is temperature-related. Anurans seem to have a greater frequency of spontaneous neoplasms than do urodeles and respond to chemical carcinogens in a manner analogous to mammalian species. Urodeles have greater cell regenerative capabilities than do anurans and paradoxically, are more refractory than anurans or mammalian species to chemical carcinogens in their proliferating regenerative blastema.