In assessing the value of systematic evaluation of extrathoracic extension for potentially resectable, non-small-cell bronchogenic carcinoma, a prospective study was conducted in 146 patients. The study protocol included computed tomographic (CT) scan of the brain and upper abdomen, abdominal ultrasonography, and whole-body bone scanning. The findings were matched with the clinical presentation, histologic features, and TN staging, having found out that non-small cell bronchogenic carcinoma does not follow a set pattern to metastasize. The rate of metastasis for adenocarcinoma is not only significantly larger (p less than 0.05) but it does not correlate with the TN staging, in contrast to what happens with the squamous cell carcinoma (p less than 0.01). None of the squamous cell carcinomas in intrathoracic stage I was found to metastasize. Twenty-one percent (4/19) of brain metastases were asymptomatic (three adenocarcinomas and one squamous cell carcinoma with multiorgan metastasis). Bone scanning detected metastasis in 3.4 percent (4/116) of the asymptomatic patients, and three of the four patients with asymptomatic metastasis had nonskeletal foci. In 61 percent (11/18) of patients with hepatic metastasis, we did not find organ-specific indicators to suspect it. The series showed a 7.5 percent incidence of adrenal metastasis. Our findings suggest the convenience of performing an upper abdominal CT scan and/or ultrasonography in all patients, except for those with asymptomatic stage I squamous cell carcinoma; we also suggest brain CT scanning for all patients with adenocarcinomas and large-cell carcinomas as well as for those with squamous cell carcinoma with neurologic symptoms, and whole-body bone scanning only in those patients with clinical and laboratory indication of possible bone involvement by metastatic disease.