Ninety-one patients with Hodgkin disease of the upper torso who had mediastinal masses were studied to determine the frequency of residual mass and the time required for resolution or stabilization of the mass. In 72 of these patients, radiographs from sufficient intervals were available for determination of the rate of regression. In 62 patients (86%), the mediastinum returned to normal width within 11 months, regardless of the size of the mass. The mediastinum returned to normal in all but one patient with small masses. The intrathoracic relapse rate did not correlate with the regression time of the masses, but relapse occurred more than twice as often in patients with residual mediastinal widening.