Biophysical modelling of DNA damage based on Monte Carlo simulation of charged particle tracks allows to describe radiation induced double-strand breaks (dsb) in a quantitative and qualitative way. Experimental and calculated data suggest that in the electron energy range from 50 eV to 1 MeV dsb can be grouped in simple and complex dsb. Complex dsb are mainly produced by low energy electrons with initial energies between approximately 200 and approximately 500 eV, whereas simple dsb are preferentially induced by energy transfers < 200 eV, which produce at least two ionizations.