The use of heavy charged particles in radiotherapy potentially represents an advance towards better local tumour control and a decrease in morbidity related to radiation injury of healthy tissues surrounding the target volume. This assertion only holds, however, if treatment planning systems give a real representation of the three-dimensional dose distribution, including physical and biological aspects, especially for heavier ions. The influence of linear energy transfer on the biological effects, its variations related to depth, particle, target tissue, position in the Bragg peak, etc. make the possible models for treatment planning extremely complex. A brief review of the problems to be addressed and some solutions is presented from the radiation oncologist's point of view.