Computed tomography (CT) is clearly more sensitive than chest radiography or conventional linear tomography in the detection of pulmonary metastases. Routine chest CT scans may reveal peripheral nodules as small as 2-3 mm, and high-resolution CT may demonstrate lymphangitic carcinomatosis. Specificity remains a problem, but attention to clinical factors, such as the type of extrathoracic malignancy (ETM), epidemiology, patient age, and prior treatment, should be of assistance. CT is useful in the evaluation of an apparent solitary pulmonary nodule or an equivocal radiographic finding. For single or multiple nodules, CT is essential for planning invasive procedures such as biopsy or surgical resection. Routine CT scanning to screen for occult metastases is indicated only for patients with ETMs that have a high propensity for metastasizing to the lungs and for which detection of pulmonary metastases would influence therapy--bone and soft-tissue sarcomas, most pediatric tumors, choriocarcinoma, nonseminomatous testicular carcinoma, and possibly advanced melanoma. Future large prospective studies evaluating individual malignancies are needed to assess the impact on long-term survival of early detection of pulmonary metastases with CT.