Seventeen patients with histologically proved bronchogenic carcinoma involving the superior pulmonary sulcus (Pancoast tumors) were evaluated by computed tomography (CT), including sagittal and coronal image reconstruction. Compared to conventional radiography, axial transverse CT images provided, in all cases, additional information regarding local tumor extension and metastatic spread. Mediastinal involvement either by lymphangitic spread or direct tumor extension was present in 11 cases. In 4 patients plain films clearly showed mediastinal disease; however, CT more clearly delineated overall tumor extent, thus facilitating improved therapy planning. In a further 4 cases CT showed mediastinal involvement after plain films had been read as normal, and in an additional 3 instances metastatic involvement was either greatly underestimated (2 patients) or overestimated (1 patient) on the plain films. Reconstructed images in sagittal and coronal planes lacked detail but facilitated a three-dimensional concept of tumor extent and relationship of tumor to adjacent structures, particularly major blood vessels.