This paper provides a survey on investigations that deal with the effects of hyperfractionation. The influence of relevant parameters on treatment results is explained. Furthermore, clinically practicable hyperfractionated treatment schedules for therapy of head and neck tumours are proposed. Clinical and experimental reports reveal that with hyperfractionation two strategies can be realised: 1. Late normal tissue reactions can be reduced without changing total dose. In this case local tumour control rate remains unchanged. 2. To enhance tumour control rates a higher total dose can be administered, if late reactions were dose limiting in the reference schedule. In this case a reduced dose per fraction and an appropriately increased total dose will leave late reactions unchanged. Applying two fractions per day the dose per fraction should not exceed 1.4 Gy. Otherwise severe acute reactions could require treatment interruption. A time interval of at least six hours between fractions reduces the risk of acute and late reactions considerably.