We evaluated the extent of possible HIV activation in human skin treated with UVB 290-320 nmâ radiation or PUVA therapy (a photosensitizing drug, 8-MOP, followed by UVA 320-400 nmâ radiation). Using the data for HIV promoter activation in vitro, we computed UVB and PUVA doses that produce 50% of the maximal promoter activation (AD50). Then, we estimated the distribution of UVB and PUVA doses in the skin. This allowed us to estimate the depth in the skin to which the HIV promoter may be activated by therapeutic UVB or PUVA doses. We found that when the incident UVB dose on the surface of the skin is 5,000 J/m2, the dose producing 50% of the maximal HIV promoter activation (AD50UVB) may be delivered to the living cells of the epidermis and even to some parts of the upper dermis. When the incident UVA dose is 100 kJ/m2 320-400 nmâ, and 8-MOP concentration in the blood is 0.1 Fg/mL (desired level), the combined PUVA doses to the mid epidermis are well below the 50% HIV promoter-activating PUVA dose (AD50PUVA). These results pertain to the advanced stages of UV therapies and suggest that HIV-activating doses penetrate deeper into the skin during UVB therapy as compared with PUVA therapy.