Abstract BACKGROUND: Ultraviolet radiation can contribute to various damages to body organs especially to skin. However, the effect of Ultraviolet B on the function of viruses, immunologic changes and antioxidants levels which protect human skin health are still unknown. We aimed to find the harmful level of UVB that can be helpful in taking preventive action against the increasing depletion of Ozone layer. METHODS: In this cross-sectional study conducted in Isfahan population, two areas with high and low levels of UVB radiation were investigated based on the information obtained from Meteorological Office. Samples in each area were selected by a cluster-sampling method. 250 persons were assigned to each group. The antioxidant capacity and glutathione peroxide level of samples were measured. Data were analyzed with Student t test by using SPSS software. RESULTS: The mean (± standard deviation) of Malondialdehide in high and low UVB radiation areas were 2.8 ± 0.32 and 1.65 ± 0.38 nmoles/ml, respectively (P < 0.001). Mean (± standard deviation) of antioxidants capacity levels were 81.6 ± 2.36 μmol/l in patients living in low UVB radiation area and 76.5 ± 2.6 μmol/l in patients living in high UVB radiation area (P < 0.0001). Glutathione Peroxide levels were 38.2 ± 1.7 and 35.3 ± 1.9 μmol/l in areas with low and high UVB radiation respectively (P < 0.0001). CONCLUSION: Findings of this study indicates that the amount of free radicals and antioxidant capacity in high UVB radiation areas are less than areas with low levels of UVB radiation. Therefore, it is suggested that necessary considerations should be taken into account for the residents of such areas in order to reduce its health damages. Keywords: Ultraviolet B, antioxidant, malondialdehyde, glutathione peroxide.