Objective: To quantify late toxicity in patients treated with intensive chemotherapy (ChT) and radiotherapy (RT) for nasopharyngeal carcinoma (NPC) and to investigate factors associated with it. Material and Methods: We retrospectively reviewed the treatment outcome in terms of moderate-severe late toxicity (MSLT) in 44 NPC patients diagnosed between 2001 and 2007. All the patients were treated with conformal RT and cisplatin containing ChT. Twenty-eight (63.6%) patients among 44 received only multidrug neoadjuvant ChT, while the remaining 16 (36.4%) patients received additional concomitant cisplatin during RT. MSLT was evaluated according to RTOG/EORTC scoring system and defined as grade 3-5 late toxicity. The median follow-up of these 44 patients was 38 months (range, 12-84 months). Statistical analyses were performed with Kaplan-Meier method and a multiple Cox's regression model. Results: The hazard probability of developing MSLT at 5 years was 49%. In univariate analyses; gender, age, histopathology, T stage, N stage and ChT schema did not have significant impact on treatment outcome in terms of MSLT. Total radiation dose to the neck, which appeared to have a paradoxical effect on late toxicity in univariate analysis turned to be insignificant in multivariate analysis. Treatment response was found to be the only prognostic factor in multiple Cox's regression analysis, which had an impact on MSLT in NPC patients. Probability of MSLT among the 12 NPC patients with less than complete response to the treatment was higher than 32 patients with complete response to the treatment (85.7% and 35.2% at 5 years, respectively; p=0.0254). Conclusion: Late toxicity in NPC patients is treatment related. Poor tumour control can be a triggering factor for development of late toxicity. Long lasting residual disease following treatment is an interesting phenomenon in NPC patients, which appears to be related with MSLT and has to be further investigated in prospective studies.