For the first time, a continuous biological dosimetry for cytotoxic solar UV-radiation has been performed in Antarctica. The biological harmful UV-radiation on the ground was measured at the German Antarctic Georg von Neumayer (70°37' S, 80°22' W) from December 1990 to March 1992 using the biofilm technique. The UV-sensitive targets were dried spores of Bacillus subtilis which were immobilized on the film surface. The UV-induced inhibition of biological activity, determined photometrically from the protein synthesized after incubation and staining, was taken as measure for the absorbed UV-dose. Films were exposed in horizontal position for time invervals ranging from 4 days during summer up to 51 and 41 days before and after the polar night respectively. The use of different cut-off filters allowed the calculation of the biologically effective UVA, UVB and the complete UV-radiation (UVA+B). The data were compared with the global radiation and the ozone column thickness indicating an increase of biologically harmful UVB radiation during austral spring at reduced ozone concentrations yielding a radiation amplification factor (RAF) of 1.4, whereas for the total UV(A+B) range the RAF amounted to 0.3.