A computer program to automatically determine lung volume and percentage of emphysema from computed tomographic (CT) chest sections was developed. To test it, the authors reviewed scans obtained in 89 patients. Any computer errors in identification of normal or emphysematous lungs were corrected manually by tracing the boundaries of the lungs or eliminating areas of nonemphysematous lung with a roller ball. The corrected values were compared with the uncorrected values. In 33 patients from the study group, lung volumes and the percentage of emphysema were calculated by using a currently available "voxel highlighting" program. Successful computerized analysis of entire lungs was performed in 1 minute, compared to more than 1 hour for manual analysis. Correlation was high (r = .99) between results obtained manually and those obtained with the computer. Although the difference between uncorrected and corrected values of the percentage of emphysema was statistically significant, this converted to a correction of only 0.1%. The computer program allowed quick, accurate, and reproducible quantification of emphysema.