Eighteen patients with Hodgkin's disease received chemotherapy and 40 Gy mantle-field irradiation. Radiation-induced lung injuries were studied 5 times during one year for each patient by chest x-ray, CT examination of the thorax and pulmonary function tests. Homogeneous and inhomogeneous densities developed within the radiations ports. They were more often and more easily detected by CT than by chest x-ray (39% vs 11% at the end of the irradiation). CT changes suggested that homogeneous lung density increase and lung nodules corresponded to the radiation pneumonitis phase, also that linear aspects and/or lung condensation aspects corresponded to irradiation-induced lung fibrosis. The displacement of the vessels and the fissures were seen more precisely by CT than by chest x-ray. There was a highly significant correlation between the number of modified areas and the increase in the coefficient of retraction (p less than 0.001).