Melanoma is an aggressive disease for which there is no effective curative treatment beyond surgical excision of the primary lesion and regional disease. Epidemiological, clinical, in vitro and in vivo studies have provided insight into the biology of the disease. This review focuses on current understanding of key molecular pathways, cellular interaction and tumor microenvironment, and the respective aberrations identified in melanoma. Common mutations and/or deregulated expressions of B-raf, N-ras, PTEN, protein kinase B (aka Akt), CDKN2A, CDK4 and MDM2 were presented. In addition to genetic abnormalities, important aspects of cellular biology including, (i) the loss of cell-cell adhesion resulting in an altered state in the relative expression of cadherins, catenins and integrins, (ii) the interaction between melanoma cells and surrounding keratinocytes, fibroblasts, and immune cells, and (iii) tumor angiogenesis and vascular mimicry, are discussed. Many ongoing clinical trials of targeted biological therapies are based on current knowledge, the outcomes are eagerly awaited.