A mini-computer configuration and its supporting software has been developed for the on-line or off-line analysis of scintillation camera lung scans with gaseous or saline-equilibrated 133-Xenon. The operating system, GAMMA, has capabilities for correction of gamma camera face uneveness, viewing of scan matrices an four isometric views, data presentation in "shades of gray" mode, and calculation of regional ventilation/perfusion ratios. Other modes of data analysis, such as iso-contour plotting and inertial moment analysis are also available. Thus far patients with various forms of pulmonary fibrosis and chronic obstructive disease have been studied by the scanning techniques. In addition, complete standard pulmonary function testing has been carried out so that correlation of scan data with results of function studies can be made. Normalization of scan data to permit direct calculation of ventilation/perfusion ratios is being attempted in order to obviate the need for volume measurements and total-system radioactivity level measurements during the procedure.