Retrospective analysis was performed with intent to evaluate prognostic factors in radiation therapy for 72 patients with histologically confirmed poorly-differentiated squamous cell carcinoma of the nasopharynx. The 10-year overall actuarial and cause specific survival rates were 36 and 40%, respectively. The median survival time was 43 months. Sixteen patients survived for more than 10 years (maximum 297 months). The five- and 10-year cause specific survival rates for Stages I, II, III and IV disease were 100 and 100%, 80 and 27%, 83 and 83%, and 38 and 31%, respectively. Two patients with Stage II disease died of a re-recurrent tumor more than seven years after their initial treatment. There was a significant difference between the survival curve for Stage I or III disease and that for Stage IV disease (P < 0.05). The patients with a T1-3 tumor had a statistically better survival rate than those with a T4 tumor (T1:T4, P < 0.001, T2 or T3:T4, P < 0.05). The patients with N0 had statistically better survival rates than those with N3 (P < 0.01). Twenty-eight patients developed loco-regional recurrence. Twenty-one patients developed distant bone metastases, most of which occurred within a year of the initiation of radiation therapy. The survival for the patients with loco-regional recurrence was nearly the same as that for the patients without loco-regional recurrence. The 10-year survival rates for patients with and without distant bone metastases were 0 and 48%, respectively (P < 0.001). Multivariate analysis revealed that the parameters influencing cause specific survival were stage categories of T and N, and adjuvant chemotherapy, whereas those influencing loco-regional recurrence were only stage categories of T and N. The only parameter to influence distant bone metastases was sex. We concluded the most important cause of failure for the patients with poorly-differentiated squamous cell carcinoma of the nasopharynx to be distant bone metastases.