To objectively reappraise the role of the chest radiograph (CXR) in the clinical assessment of emphysema, we compared a standardized reading of CXR with both a visual scoring and a quantitative analysis of high resolution computed tomography (HRCT) of the chest in 46 consecutive patients with chronic obstructive pulmonary disease (COPD) and fixed expiratory airflow limitation. CXR were scored for signs of overinflation and pulmonary vascular deficiency by three independent observers. HRCT scans were independently scored for extent of emphysema and for both severity and extent of emphysema. In 28 of 46 patients, inspiratory and expiratory HRCT scans were analyzed quantitatively by measuring the mean CT number in Hounsfield Units (HU) and the percentage of lung area with CT numbers < -900 HU. Quantitative CT data were compared with reference values obtained in seven normal nonsmokers. The CXR score of emphysema showed a highly significant interobserver reproducibility and correlated linearly (p < 0.001) with HRCT visual scores and quantitative data from both inspiratory and expiratory CT scan. CXR score correlated with functional indices of airflow obstruction, overinflation, and impaired lung diffusing capacity in a way comparable to that obtained by using qualitative and quantitative CT data. Patients with no signs of emphysema on CXR had mean expiratory CT numbers within normal range and a fraction of lung area with CT numbers < -900 HU on expiratory scan not exceeding 15% of total cross-sectional area. The latter value was consistently greater than 15% in patients with CXR score > 0.(ABSTRACT TRUNCATED AT 250 WORDS)