Recent studies in our laboratory have identified novel molecular diagnostic and prognostic markers based on analyses in large cohorts of melanoma patients. These markers were initially derived from gene expression profiling analyses of distinct stages of melanoma progression. Immunohistochemical analyses confirmed the differential expression of these markers, and immunohistochemistry-based multimarker assays were developed to assess melanoma diagnosis and prognosis at the molecular level. In this chapter we review the development of these assays and the methodologies used to assess marker expression in both nevi and primary melanomas.