摘要： Ultraviolet (UV) radiation is recognized as an essential risk factor due to its dual role of affecting the human skin. Primarily, it is required for natural vitamin D synthesis in the skin which is indispensable for human health in many constructive ways. On the other hand, UV radiation acts as a non-specific damaging agent and a mutagen as well. UV radiation has potential to cause both cancer initiation and progression. Excessive and repeated exposure to UV is associated with health risks, including pigment changes, wrinkle formation, atrophy, and malignancy. Epidemiologically and molecularly UV is linked to DNA damage, either directly or indirectly via oxidative injury resulting in various types of skin cancer. Genetic factors also stimulate threat of UV-mediated skin anomalies. This chapter emphasizes on genetic and molecular mechanisms of pigmentation, tanning, DNA damage and repair, Melanocortin 1 receptor (MC1R) gene expression, photoproduct formation, and p53 mutation.