Obesity has been implicated in several diseases including cancer, however, the relationship of obesity and susceptibility to ultraviolet (UV) radiation-caused skin diseases has not been investigated. As UV-induced oxidative stress has been implicated in several skin diseases, we assessed the role of obesity on UVB-induced oxidative stress in genetically obese Lep ob /Lep ob (leptin-deficient) mice. Here, we report that chronic exposure to UVB (120 mJ/cm 2 ) resulted in greater oxidative stress in the skin of obese mice in terms of higher levels of H 2 O 2 and NO production, photo-oxidative damage of lipids and proteins, and greater depletion of antioxidant defense enzymes, like, glutathione, glutathione peroxidase and catalase. As UV-induced oxidative stress mediates activation of MAPK and NF-κB signaling pathways, we determined the effect of UVB on these pathways in obese mice. Exposure of obese mice to UVB resulted in phosphorylation of ERK1/2, JNK and p38 proteins of the MAPK family. Compared to wild-type mice, the obese mice exhibited higher levels of phosphorylation of these proteins, greater activation of NF-κB/p65, and higher levels of circulating proinflammatory cytokines, including TNF-α, IL-1-β and IL-6, on UVB irradiation. Together, our study suggests for the first time that obesity in mice is associated with greater susceptibility to UVBinduced oxidative stress, and therefore may be a risk factor for skin diseases associated with UVBinduced oxidative stress.