An IARC Working Group has assessed the available evidence relating to possible detrimental health effects of exposure to artificial ultraviolet radiation through use of indoor tanning facilities, in particular whether their use increases the risk for skin cancer. Epidemiologic studies to date give no consistent evidence that use of indoor tanning facilities in general is associated with the development of melanoma or skin cancer. Knowledge of levels of UV exposure during indoor tanning is very imprecise. Moreover, early studies published had low power to detect long-term associations with artificial UV exposure that become evident only following a prolonged lag period. However, the data showed a prominent and consistent increase in risk for melanoma in people who first used indoor tanning facilities in their twenties or teen years. Limited data suggest that squamous cell carcinoma is similarly increased after first use as a teenager. Artificial tanning confers little if any protection against solar damage to the skin, nor does use of indoor tanning facilities grant protection against vitamin D deficiency. Data also suggest detrimental effects from use of indoor tanning facilities on the skin's immune response and possibly on the eyes (ocular melanoma).