Melanoma rates have increased in populations that are mainly European. The main etiologic factor is ultraviolet radiation, from the sun as well as artificial tanning devices. Host factors such as skin color, number of nevi, hair and eye color and tanning ability are critical factors in modifying an individual's response to the sun. Genetic factors interact with host factors and environmental factors to increase risk. This review summarizes our current knowledge of environment and genetics on melanoma risk and on gene-environment interaction.