Radiation therapy represents an extensively experimented treatment modality for head and neck tumors. Recent studies have documented a close dependence of clinical results, especially in terms of local control and toxicity, on the radiation therapy quality. Thus the effort to improve the results of conventional radiotherapy has been achieved with the identification of new therapeutic modalities (non conventional fractionation, conformal therapy, fast neutron radiotherapy, concomitant or neoadiuvant chemotherapy) as well as with constant optimization of the accuracy of used procedures. Among them the following should be mentioned: 1) the systematic use of immobilization systems which enable a significant reduction in positioning errors; 2) checks before and during treatment by portal imaging which enable to identify and correct a relevant percentage of inaccuracies; 3) "in vivo" dosimetry which enables an overall assessment of treatment accuracy. The general evolution of the radiobiological knowledge occurred in recent years has introduced into radiotherapy of head and neck tumors new schemes of fractionation and new modalities of combination with other therapeutic procedures. Furthermore, while the widespread use of complex irradiation procedures calls for the urgent need of quality assurance of radiation treatments, this is by all means a mandatory requirement even in the most conventional clinical practice.