We describe Monte Carlo codes that simulate, event by event, the interaction of energetic electrons with a double-stranded DNA molecule and with the condensed water surrounding it. Both direct and indirect effects are treated explicitly . The cross-sectional input necessary in the transport codes was obtained via quantum-mechanical calculations of the dielectric response function epsilon(q, omega), of polycytidine. For each inelastic event on DNA we score the energy deposited locally, the position of the event and the moiety that underwent that event. This information provides a detailed picture of the spatial disposition of molecular alterations for DNA exposed to ionizing radiation.