Abstract： Objective To investigate the feasibihty and efficacy of dose escalation using three-dimensional conformal radiotherapy(3D-CRT) boost technique for locally recurrent nasopharyngeal carcinoma(NPC) in a randomized study.Methods Thirty-six patients with locally recurrent NPC were treated between August 2004 and August 2007 at our institution.Patients were treated with exlemal-beam radiotherapy using small shaped fields to 50 Gy/25 fraetion/5 weeks,followed by a 3D-CRT boost to the gross tumor region.Patients were randomized to three boost dose levels:16 Gy(4 Gy×4 fractions) for Group Ⅰ:20;Gy(4 Gy×5 fractions) for Group Ⅱ;and 24 Gy(4 Gy×6 fractions) for Group Ⅲ.All boost doses were delivered as 3 fractions per week.Twelve patients were enrolled in each group.Median follow-up was 27 months (range 14～44 months).Results There was no significant difference among the three groups in acute and late toxicity.Overall 3-year survival rate was 65%,3-year local recurrence-free survival rate was 45%,and 3-year disrant metastasis rate was 10%.The local recurrence free survival was significantly hisher(72%) for the high-dose Group Ⅲ than that for Groups Ⅰ and Ⅱ.The 3-year distant metastases rates were no significant difference in Group Ⅰ,Ⅱ,Ⅲ respectively.There was no significant difference in the 3-year overall survival rate among the three groups.Univariate analysis revealed that skull base invasion and pathology were significant prognostic factors furoverall survival rate.Conclnsion Re-irradiation with hish-dose 3D-CRT boost results in high local control rate and acceptable toxicity in with recurrent NPC.Dose escalation to the boost volume to 74 Gy(54 Gy+24 Gy boost) results in improved recurrence-free survival to lower doses.