UV excimer lamps are efficient and economical narrowband sources of UVB and UVC radiation. Potentially, these lamps may be used in bacterial disinfection or in minor cosmetic procedures, but safety tests are necessary. For this purpose, cellular damage induced by the UV radiation is assessed. 3T3 mouse fibroblasts are used as a model system. It is found that lethal damage occurs above a certain wavelength-dependent threshold dose. Furthermore, the antioxidant balance of the cells is influenced; glutathione levels are usually depleted, both under and above the lethal threshold. A striking increase of glutathione level is observed after UVC irradiation. This is attributed to an enhanced repair activity as a response to acute oxidative stress induced by UVC. In contrast to UVC, low-power irradiation with UVB seems to induce very little cellular damage.