Mammalian cell culture research has been progressively helpful in investigating the influence of different environmental conditions on viability, productivity and cytogenetic effects. From the obtained results risk was extrapolated to man. For testing toxicity testing a number of methods have been developed which base on either the viability of cell populations or on the proliferative capacity of single cells.We developed the biological UV dosimeter RoDos, which weights the UV radiation according to its DNA damaging potential. The RoDos dosimeter is based on rodent cells growing on a UV-transparent petriPERM® foil and a special device which allows irradiation with different doses of UV light, assuring cellular growth under identical spatial arrangement of the cells. Cells under investigations are Chinese hamster ovary cells AA8 (repair proficient) and UV5 (defective in nucleotide excision repair) grown in monolayer culture. Cells growing on the petriPERM® foil were exposed in the RoDos device to increasing doses of UVC (254 nm) or simulated sunlight (SSL) of various UVB/UVA proportions. After exposure cells were further incubated for three days, fixed and stained. The influence of irradiation on "cell growth" is determined by image analysis as relative luminance (L) of the irradiated to unirradiated areas of the petriPERM® dish. The resulting action spectra for cell growth inhibition after exposure to simulated sunlight of different qualities were measured with the RoDos device for repair-proficient AA8 cells. The radiation sensitivity of the rodent cell system decreases with longer wavelengths of simulated sunlight, having different proportions of UVB and UVA.