We studied 60 male patients who had concurrent chest films (CXR), computed tomography scans (CT) and pulmonary function tests (PFT) to assess the sensitivity of CT and conventional films in detecting emphysema compared with PFT. We also sought to determine whether emphysema could be diagnosed by CT in patients with normal pulmonary function. Using a method similar to that proposed by Bergin, we scored the severity of emphysema depicted by CT, and using arterial deficiency and bullae as criteria, we estimated the degree of emphysema on CXR. There was a significant inverse correlation between CT scores for emphysema and percentage predicted values of DLco/VA (r = -0.650), FEV1 (r = -0.552), and FVC (r = -0.409), (P less than 0.001). A significant but smaller correlation also was noted with the CXR scores and percentage predicted: DLco/VA (r = -0.564), FEV1 (r = -0.454), and FVC (r = -0.355), (P less than 0.005). When decreased diffusion capacity and airway obstruction were used as functional criteria of emphysema, CT was as sensitive as PFT and more sensitive than CXR in detecting emphysema (96% vs. 68%). There was CT evidence of emphysema in 69% (24/35) of patients who did not have functional findings of emphysema. In 12 pathologic specimens available for review, 11 had emphysema by CT and pathologic examination; one patient had centrilobular emphysema undetected by CT. We conclude that CT is as sensitive as PFT in detecting emphysema and more sensitive than conventional radiography. CT may be more sensitive than PFT in detecting mild emphysema.(ABSTRACT TRUNCATED AT 250 WORDS)