Melanoma is one of the most aggressive forms of skin cancer. The management of melanoma is evolving rapidly due to an improved understanding of the molecular heterogeneity of this disease and the development of effective, personalized, targeted therapy strategies. Although previous classification systems were based predominantly on clinical and histologic criteria, there is now a strong rationale for adding molecular markers to the diagnostic evaluation of these tumors. Research has shown that the types and prevalence of genetic alterations vary among melanoma subtypes. Thus, rational molecular testing should be based on an understanding of the events that are likely to occur in a given tumor and the clinical implications of test results. This review summarizes the existing data that support the rationale for molecular testing in clinically defined melanoma subtypes. Emerging challenges and controversies regarding the use of various molecular testing platforms, and their implications for clinical testing, are also discussed.