BACKGROUND An International Atomic Energy Agency (IAEA)-sponsored, multi-institutional prospective randomized trial was conducted to clarify whether the combination of hyperthermia and radiotherapy improves the local response rate of locally advanced non-small cell lung cancer (NSCLC) compared with that obtained by radiotherapy alone. METHODS Between October 1998 and April 2002, 80 patients with locally advanced NSCLC were randomized to receive either standard radiation therapy alone (RT) or radiation therapy combined with hyperthermia (RT + HT). The primary endpoint was the local response rate. The secondary endpoints were local progression-free survival and overall survival. RESULTS The median follow-up period was 204 days for all patients and 450 days for surviving patients. There were no significant differences between the two arms with regard to local response rate (P = 0.49) or overall survival rate (P = 0.868). However, local progression-free survival was significantly better in the RT+HT arm (P = 0.036). Toxicity was generally mild and no grade 3 late toxicity was observed in either arm. CONCLUSIONS Although improvement of local progression-free survival was observed in the RT+HT arm, this prospective randomized study failed to show any substantial benefit from the addition of hyperthermia to radiotherapy in the treatment of locally advanced NSCLC.