Imaging assessment of the lumbosacral spine following surgery is complex and depends upon several factors, including the anatomy of the patient, the surgical procedure and the disease process for which it was performed, the age of the patient, the biomechanical condition of the underlying cortical and cancellous bone, intervertebral disc and musculoligamentous tissues, the time since surgery procedure and the duration and nature of the postsurgical syndrome. Depending upon these factors, one or a combination of complementary imaging modalities may be required to demonstrate any clinically relevant abnormality, to assist the surgeon in deciding if repeat surgery is necessary, its nature and at which vertebral level(s) it should be directed. This review stresses the important role of MRI following lumbar discectomy, intervertebral fusion and/or instrumentation in achieving the most beneficial and timely outcome in the patient presenting with an acute, subacute or chronic failed back surgery syndrome.