The Radiation Therapy Oncology Group reported a maximum tolerated dose of 74 Gy for patients with non-small cell lung cancer (NSCLC); however, it was unclear whether this dose could be safely administered to Asian patients due to differences in their physique compared to Western patients. We therefore conducted a modified Phase I trial to determine whether 70 Gy could be safely delivered to Chinese patients with NSCLC undergoing 3D-conformal radiation therapy (3D-CRT) with concurrent chemotherapy. Previously untreated NSCLC patients received 3D-CRT (2 Gy/day, 5 fractions per week). Three dose levels were examined: 62, 66 and 70 Gy. Two cycles of concurrent chemotherapy (vinorelbine and carboplatin) were started on the first day of radiation therapy. Dose-limiting toxicity (DLT) was defined as severe or life-threatening side effects that altered the continued implementation of chemoradiotherapy. Among the 19 patients recruited in this study, most of the haematologic and non-haematologic toxicities were mild to moderate and clinically manageable. Only one patient, in the 70 Gy cohort, experienced a DLT of Grade 3 radiation-induced pneumonia. The overall response rate was 77.8% (14/18). The median progression-free survival (PFS) was 12 months, and the 1-year PFS was 37.6%. Our results support both the feasibility of incorporating 3D-CRT with concurrent vinorelbine and carboplatin and a dose escalation to 70 Gy for Chinese patients with NSCLC, based on the acceptable toxicity and encouraging overall response and survival rates. A further evaluation of this regimen in a prospective Phase II trial is ongoing.