BACKGROUND AND PURPOSE: To assess the feasibility and efficacy of accelerated 66-Gy postoperative radiotherapy (PORT) using a single-fraction regimen from Mondays to Thursdays and a concomitant boost on Friday afternoon sessions in patients with locally advanced head and neck cancer (LAHNC). PATIENTS AND METHODS: Between December 1997 and June 2002, 89 consecutive patients with pT1-pT4 and/or pN0-pN3 LAHNC were included. PORT was indicated in patients with positive surgical margins, T4 tumors, or extracapsular nodal infiltration. RT consisted of 66 Gy (2 Gy/fr) in 5 weeks and 3 days. Median follow-up was 21 months (range 2-59). RESULTS: Acute morbidity was acceptable: grade 3 mucositis in 20 (22%) patients, grade 3 dysphagia in 22 (25%) patients, and grade 3 skin erythema in 18 (20%) patients. Median weight loss was 2 kg (range 0-14.5). No grade 4 toxicity was observed. Late effects included grade 3 xerostomia in 6 (7%) patients, and grade 3 edema in 2 (2%) patients. Median time to locoregional relapse was 10 months (range 2-21). Two-year overall, cause-specific, and disease-free survival rates were 70% (95% confidence interval (CI) 59-81), 75% (95% CI 64-86), and 63% (95% CI 52-74), respectively. The 2-year actuarial locoregional control rate was 80% (95% CI 70-90). Distant metastasis probability at 4 years was 38% (95% CI 20-56). Multivariate analysis revealed that pT-classification (pT1-2 vs. pT3-4) and extranodal extension (0, 1 vs. 2 or more) were the two factors independently influencing the outcome. CONCLUSIONS: We conclude that reducing the overall treatment time using an accelerated PORT schedule including a once-weekly concomitant boost (six fractions per week) is easily feasible with excellent local control. Acute and late RT-related morbidity is acceptable. Given the disease progression pattern (distant metastases), adjuvant chemotherapy should be considered.