Melanoma incidence and morality rates are increasing in most countries throughout the world where they are being recorded. The annual incidence rates have increased in the order of 3-7% in fair-skinned populations in recent decades. The mortality rates have increased at a rate lower than for incidence. This has been attributed to educational programs designed to improve the early detection of melanoma, as the treatment of melanoma has not changed substantially in recent decades. There has been a decrease in the thickness of melanoma with an increasing proportion of thin melanomas at diagnosis. Causation of melanoma is a combination of constitutional risk factors of which skin colour is the major factor. The presence and number of common acquired and dysplastic melanocytic naevi is also a major constitutional risk factor in fair-skinned people. The only environmental risk factor that has been shown consistently is exposure to sunlight, particularly large doses of sunlight sufficient to cause sunburn in childhood that will be remembered many years later. However, recreational activity leading to sunburn in adulthood is also associated with risk. To date, no other environmental factors have been shown epidemiologically to be clearly associated with risk of melanoma. Recent epidemiological data from some studies suggesting that there is an increased risk of melanoma in sunscreen users requires further explanation.