Patients of Hutchinson-Gilford Progeria Syndrome (HGPS) display a rate of aging up to ten times that of normal human populations. It might be expected that HGPS cells would have a decreased ability to repair DNA damage through the cell cycle as compared to normal cells such as those of the BJ cell line since DNA damage accumulation is a hallmark phenotype of aging. On earth, we are exposed to far more ultraviolet-B (UV-B, 280-315 nm) and UV-A (315-400 nm) than UV-C (100-280 nm) radiation, since the latter is filtered-out by the atmospheric ozone layer. The relative sensitivity of prematurely aging HGPS cells to UV-B irradiation is unknown. It was hypothesized that the normal fibroblast cell line (BJ) would exhibit a higher rate of DNA repair and a higher level of cell viability after exposure to ultraviolet radiation than would be observed with the HGPS cells, and that these differences would be greater as the HGPS cells age in culture. A Cell-Titer Blue Viability Assay (Promega) was used to determine the effect of UV-B and UV-C on metabolic activity, an indicator for cell viability, in HGPS, BJ, and A549 (a human lung carcinoma) cells. A translesion DNA synthesis protein, pol-η, and several other DNA transcription and repair-related proteins also were hypothesized to be altered in the HGPS cell line, both before and after UV-induced DNA damage, as compared to the BJ cell line. Western blotting was used to monitor these proteins in BJ and HGPS cells following UV-C exposure. No differences in short-term viability were observed between BJ and HGPS cells, reflecting similarities in their repair abilities on the cellular level; however, there were significant differences in long-term viability. Enzyme Linked Immunosorbant Assays (ELISA) revealed a significant difference in DNA repair at the molecular level. Moreover, Western blotting revealed differences in the amounts of several repair-related proteins following UV exposure, including pol-η, an important trans-lesion synthesis protein. Although the difference in DNA repair did not appear at the cellular level, it is apparent that HGPS cells show a greater sensitivity to both UV-B and UV-C irradiation as compared to normal BJ fibroblasts and A549 carcinoma cells.