Autopsies on 102 patients dying with bronchogenic carcinoma over an 11-year period revealed that 37.3% had pulmonary metastases. Review of the pathological evidence in questionable cases supported the validity of the diagnosis. This rather high figure is paralleled by the findings of others quoted in the literature. Dissemination in the lungs appears to take place early with respect to the time of diagnosis. Seventeen of 49 patients (34.7%) who died within 1 month of tissue diagnosis already had additional pulmonary foci. It was possible to identify intrapulmonary spread radiographically in over half of the cases despite the prevalence of concomitant pulmonary disease. Hence, x-ray examination is a useful means of establishing the existence of such metastases in pursuing clinical trials.