The distributions of ventilation, lung volumes and perfusion were studied in 56 healthy non-smoking Finnish adults to get reference values for a computerized 133-Xe radiospirometer with 16 detectors and moveable designed collimators (Valmet BI 1200). The age of the subjects ranged from 20 to 60 (mean 36.5, SD 9.1) years. Thirty-one of them were men. In addition, the reproducibility of the method was tested in 13 patients with pulmonary diseases. The measurements were made with the subjects in supine position. The studied variables showed no correlation with sex or age. The interpulmonary and intrapulmonary percentage distributions between 16 pulmonary subareas were calculated for the following variables: ventilation (V) (assessed from wash-in curves), functional residual capacity (FRC), vital capacity (VC), total lung capacity (TLC), wash-out time during tidal breathing (T1/2 V), perfusion (Q) (at TLC level), wash-out time after breath-holding during the perfusion study (T1/2 Q), specific ventilation (V/FRC), specific perfusion (Q/TLC), and V/Q ratio. The percentage proportion (mean and SD) in the right lung of V was 50.5 (2.6), of FRC 51.7 (2.1), of VC 51.0 (1.8), of TLC 51.1 (1.7), and of Q 50.8 (3.0). Apical parts of the lungs showed smaller functional proportions than the other parts. There was a significant tendency to increasing basal and decreasing apical proportions of V, VC, TLC and FRC with increasing height and weight. Coefficients of variation (CoV) of the distribution indices for the whole lung varied between 1.9 and 5.0%. We suggest that the distribution data obtained here are helpful in clinical work when evaluating the distributions in patients studied with the Valmet BI 1200 radiospirometer.