A randomized clinical trial has been earned out since January 1991, comparing conventional radiotherapy 60 Gy/30 fractions/6 weeks with continuous hypefractionated, accelerated radiotherapy 54 Gy/36 fractions/ 12 days in locally advanced non-small cell carcinomas of the lung. With continuous, hyperfractionated, accelerated radiotherapy regime a fraction size of 1.5 Gy has been used, and 3 fractions have been given with a time interval of 6 hours on each of 12 consecutive days without interruption for the weekend. Early and late radiation effects were compared for each group in 25 patients (Conventional radiotherapy group 12 patients, continuous hyperfactionated accelerated radiotherapy group 13 patints). The most important difference in acute reactions has been the increased incidence of esophagitis in the continuous hyperfractionated accelerated radiotherapy group. No significant in subacute and late radiation effects has been observed.