Since 1997 GSI operates a pilot project to treat tumours in the head and neck region with scanned beams of swift carbon ions. In order to exploit the unique physical and radiobiological properties of ion radiation, a dedicated treatment planning system (TPS) is mandatory. For this purpose the TRiP98 code package has been developed for well over a decade, in order to calculate and optimize absorbed as well as biological dose distributions for scanned ion beams. In collaboration with the DKFZ Heidelberg, the Radiological University Hospital Heidelberg and the FZ Rossendorf more than 400 patients have been planned and treated so far. This article will summarize the current capabilities of the TRiP98 TPS as well as future challenges and developments.