Acute and subacute infection in the mediastinum, though rare, is associated with a substantial mortality which increases with delay in diagnosis. The conventional radiographic and computed tomographic studies of 14 patients with proven infective mediastinitis were reviewed in an attempt to identify their relative roles in its diagnosis. Signs of infection demonstrated by computed tomography (CT) included abscess formation, mediastinal masses, soft tissue collections contiguous with other infected compartments and areas of diffuse mediastinal infiltration with fat plane loss without prominent lymphadenopathy. The anatomy and extent of the infection was well delineated by CT in all patients. In nine cases this information affected clinical management, facilitating percutaneous drainage of the abscess in three. In five patients, information from CT did not alter clinical management.