There are currently more than 100,000 anterior cruciate ligament (ACL) reconstructions performed annually in the United States. The overall rate of success of ACL reconstruction in terms of restoration of stability, loss of sensation of giving way and relief of symptoms is reported between 75% and 90% in the literature. Approximately 8% of these patients have an unsatisfactory result due to recurrent instability and graft failure. An ACL reconstruction failure may consist of a combination of subjective factors of pain, instability, or stiffness as well as objective findings of laxity, progressive degenerative changes, or loss of motion. For many of those patients who experience a failure following an ACL reconstruction, revision ACL reconstruction is indicated to provide the patient with a stable knee, to prevent further injury to the cartilage and menisci, and to improve patient function. Operative considerations include the timing of the surgery, graft selection, and surgical technique. Other considerations include the treatment of combined instabilities, the treatment of pre-existing meniscal or articular pathology, and the necessity of performing any corrective limb realignment procedures. This article will discuss the mechanisms of failure of ACL reconstructions, will provide an approach to patients with ACL reconstruction failures, and will discuss the rationale for primary grafting and for staged revision surgery.