Extranodal natural killer/T-cell lymphoma (ENKTL) is an aggressive neoplasm with a poor outcome. Asparaginase-based regimens are recommended for patients with advanced-stage or relapsed/refractory ENKTL. We retrospectively investigated the efficacy and toxicity of combined gemcitabine, oxaliplatin, and pegaspargase (P-gemox) in these patients. A total of 35 patients with newly diagnosed stage III-IV, relapsed or refractory ENKTL were treated with 2 to 8 cycles of P-gemox: gemcitabine (1250 mg/m(2)) and oxaliplatin (85 mg/m(2)) injected intravenously and pegaspargase (2500 IU/m(2)) injected intramuscularly on day 1 and repeated every 2 weeks. Upon completion of treatment, the overall response rate was 80.0%, with a complete response in 51.4% of patients. The 1-, 2- and 3-year progression-free survival rates were 45.0%, 38.6% and 38.6%, and overall survival rates were 76.8%, 64.7% and 64.7%, respectively. Patients who attained a complete response showed better progression-free survival than those without a complete response (p = 0.01). The major adverse effects were hematologic toxicity and liver dysfunction. Grade 3/4 leucopenia and neutropenia occurred in 40.0% of patients. No treatment-related deaths occurred. These results indicate the P-gemox regimen is a safe and effective treatment for patients with newly diagnosed advanced-stage or relapsed/refractory ENKTL. We anticipate future prospective trials will confirm the efficacy.