The author provides current data about mechanisms of the damaging effect of ultraviolet rays on our skin as well as describes constitutional skin phototypes (based on the Fitzpatrick scale) and clinical stages of skin photoaging (based on the Glogau classification system). The author assessed the extent of changes in the cell structure at different epithelial tumors of skin developing against the background of progressing skin photoaging. The study used molecular markers showing the extent of proliferative activity and differentiation of keratinocytes (anti-Ki67 antibodies, PCNA, P53, Bcl-2, matrix metalloproteinases MMP-1, -9 and their endogenous inhibitors Т1МР-1 ,-2) as their interpretation helps understand the processes of induction and promotion of oncogenesis induced by ultraviolet rays. The author also describes methods of photoaging prevention and treatment.