This is a prospective evaluation of the use of MR angiography (MRA) at 1.5 T in the assessment of intrathoracic masses. Two-dimensional (2D) MRA was obtained sequentially by means of a fast low angle shot (FLASH) technique (repetition time 30 ms, echo time 10 ms, flip angle 30 degrees) one slice per breath-holding. An automated control procedure and instantaneous image reconstruction permitted constant monitoring of the image quality and tailoring of the timing of the scans to each patient's breathing capacity; MRA was successfully completed in all patients. Two-dimensional FLASH angiography was postprocessed into three-dimensional (3D) MR angiography (projections) by a maximum-intensity-projection algorithm; a 3D spatial impression of the MRA was achieved by obtaining 3D MRAs from different viewing angles and by viewing these in a cine-loop. Superimposition of vessels was avoided by creating angiograms of interest of a specific anatomic region. Fifteen patients with malignant or benign intrathoracic tumor were evaluated; their MR findings were correlated with chest radiography, conventional angiography, bolus enhanced CT, and/or perfusion scintigraphy. Magnetic resonance angiography revealed stenosis, distortion, and displacement of vessels by tumors as well as distal perfusion defects caused by proximal tumors. The MRA findings were readily accepted by our clinical colleagues and incorporated into their surgical planning. We believe MRA to be a promising complement to MR imaging in the assessment of intrathoracic masses.