Objective To evaluate MR appearances of normal and injured anterior cruciate ligament(ACL).Methods The MR findings of normal ACL in 16 cases and ACL tear in 15 cases were reviewed retrospectively.Results Normal ACL appeared as a flat band with low signal intensity on T1 and T2-weighted imaging. The injured ACL can appeared as interruption in continuation(n=5), irregular shape(n=1),abnormal direction(n=2) and increased in signal intensity(n=7).Conclusion MRI is a accurate and noninvasive diagnostic method for ACL tear.