The purposes of this study were to quantitatively evaluate a free-breathing three-dimensional (3D) variable angle uniform signal excitation (VUSE) magnetic resonance angiography (MRA) technique in normal volunteers, to demonstrate breathold 3D VUSE MRA in a normal volunteer, and to investigate the ability of the free-breathing 3D VUSE MRA technique to quantify differential flow in lung transplant patients. A free-breathing 3D VUSE MRA pulse sequence was run on the right lungs of 15 normal volunteers and both lungs of eight single or double lung transplant patients. A breathold scan was also used on one volunteer. No contrast agents were used. Normal lung MRA images were analyzed for maximum level of branching observed and minimum distance between distal vessels seen and the pleura. In patients, differential flow was determined with a program that counted the number of MRA pixels over a threshold signal level in each lung. These values were compared to radionuclide perfusion (Q) scan results. Average observed branching order in normal lung images was 5.9 +/- 0.7. Average distance between the most peripheral vessels seen and the pleura was 0.9 cm. Differential blood flow measured by pulmonary MRA was well correlated with that measured by Q scan (R2 = 0.84, p < 0.005). In addition to providing good visualization of normal pulmonary vessels, this technique was demonstrated to provide accurate estimates of differential blood flow in lung transplant patients free of serious lung scarring.