Background and purpose: In this prospective study, the effect of a second course of primary radiotherapy on locoregional control, survival and toxicity was investigated, in patients who underwent a second course of high dose irradiation for second primary or locoregional recurrent squamous cell head and neck carcinoma (HNSCC) in a previously irradiated area. Patients and methods: A total of 34 patients with second primary (n=26) or locoregional recurrent (n=8) tumours were treated with a second course of high dose radiotherapy. Patients were selected for re-irradiation in case of inoperable and/or unresectable tumours. In most cases, the target volume for re-irradiation was confined to the gross tumour volume (GTV). No elective radiotherapy was applied in the former high-dose area. A total dose of 46 Gy was applied to elective areas with a boost up to 60 Gy with conventional fractionation. The median follow-up period was 32 months. Results: The locoregional control rate after 2 years was 27%. The 3-year overall survival was 22%. The most frequently reported acute side-effect was acute mucositis resulting in swallowing complaints. Pharyngeal and oesophageal late morbidity was also the most important late side-effect. In general, acute and late radiation-induced morbidity remained within acceptable limits. Conclusions: In conclusion, primary re-irradiation appears to be feasible in terms of acute and late radiation-induced toxicity. To improve outcome in terms locoregional control and survival, future studies should be focussed on optimising radiation schedules and the addition of concomitant chemotherapy.