The theory of nuclear equivalence proposes that specialized somatic cells of metazoans possess a gene pool identical to that present in the zygote nucleus. We examine this theory on the basis of nuclear transplantation experiments in amphibian oocytes and eggs. This procedure has the potential to test the entire genome and to evaluate the problem of nuclear equivalence in the context of a functioning organism. Nuclear transplantations from several differentiated somatic cell types into oocytes and eggs have revealed that their nuclei still contain the genes required for the development of prefeeding tadpoles. In addition, erythrocyte nuclei have directed the formation of feeding tadpoles that advanced to stages of hind limb bud. Thus, the genome of several differentiated somatic cells displays genetic multipotentiality. Although evidence for the genetic totipotency of specialized somatic cells is lacking, the results of our recent experiments suggest that the genetic totipotency of at least some differentiated somatic cell types still remains a tenable hypothesis.