Magnetic Resonance Imaging (MRI) has been applied to musculoskeletal pathoanatomy and has proved to be useful in the detection and characterization of knee pathology. Thirty-two acutely injured knees and 8 normal knees were examined. The images were obtained in the Diagnostic Centre RMRC of Naples on a 0.5 T superconductive magnet system, using a surface coil and a spin-echo pulse sequence (SE 600/28 ms). The examined limb was immobilized and bent at 8-10 degrees, extrarotated for the examination of the anterior cruciate ligament (ACL) only. Images were obtained on a 256 x 256 matrix and had a 2 or 4-mm thickness. MRI clearly showed all the anatomical structures. The anterior and posterior cruciate ligaments (ACL and PCL) and the patellar ligament were shown by sagittal SE images through the intercondylar notch; the tibial and fibular collateral ligaments (TCL and FCL) were evaluated on coronal SE images; the articular capsula and menisci on axial transverse SE images. Objective criteria for ACL and PCL tears were: lack of continuity of the signal and change in signal intensity; in meniscal pathology, menisci with small linear regions of increased signal or with grossly truncated shape were interpreted as tears. Preliminary results of this study indicate that MRI together with clinical evaluation may be an useful non-invasive procedure in the assessment of acute injuries of the knee.