Tumor bulk has been recognized as an important prognostic factor in the treatment of malignancy. The purpose of the present study is to investigate the prognostic value of tumor volume in nasopharyngeal carcinoma. Sixty patients with nasopharyngeal carcinoma were included in this study. Tumor contour was outlined on each of the computed tomography (CT) images using an image analyzer. The primary tumor volume (PTV) and nodal tumor volume (NTV) were calculated by a summation-of-areas technique, and the maximal perimeter of primary tumor (MPP) was measured. The loco-regional control rates and disease-specific survival rates were analyzed according to several variables. The patients had a 5-year local control rate of 75.5%, 5-year nodal control rate of 74.6%, and 5-year disease-specific survival rate of 60.2%. Large PTV ( > 30 cm3) was associated with a significantly lower local control (p=0.005). Large NTV ( > 5 cm3) was associated with a significantly lower nodal control (p=0.019) and lower disease-specific survival (p=0.046). Large MPP ( > 18 cm) was associated with a significantly lower local control (p=0.017). In multivariate analysis, the PTV and NTV were found to be independent factors in predicting the local (p=0.015) and nodal (p=0.039) control, respectively. The NTV (p=0.012) and cranial nerve involvement (p=0.009) were factors that predicted disease-specific survival. Our results suggest that the estimation of tumor volume may identify a subgroup of patients with a greater risk of loco-regional failure and can be used to refine the current staging system.