Our overall objective is to determine the relative contributions of host genetic, endocrine and cell mediated immune systems to the natural history of Sinclair swine cutaneous malignant melanoma (SSCM). Three hypotheses will be tested: a. That no more than three (3) loci are involved in the expression of SSCM, and that these loci can be identified. b. Amplification, rearrangement and overexpression of genes may be informative markers for transformation and regression. c. Temporal, relative changes in the expression of growth factors and cytokines, possibly modulated by estradiol, alters the natural history of SSCM. We suggest that identification of the mode of inheritance of SSCM, the genetic loci which control its expression, and those additional causal actions which regulate transformation and regression will provide new critical information on the developmental biology of human melanoma.