Early recognition and determination of the cause of renal failure in patients with ESLD can be difficult because of the potential interplay among various factors and the wide array of differential diagnoses. A systematic approach, however, assists clinicians to identify common and potentially reversible causes of ARF. It is crucial to distinguish patients with functional renal failure, such as HRS, from those with advanced irreversible renal disease. Isolated liver transplantation is the treatment of choice for the former, and CLKT may be a therapeutic option for the latter. Because of the ever-increasing shortage of donor organs, CLKT must be used judiciously. Kidney biopsy may resolve diagnostic dilemmas. Management of renal complications post-OLT remains a challenge for the physician caring for transplant patients. Modification of nephrotoxic immunosuppressive regimens to avoid postoperative ARF/CRI has met with variable results. Azathioprine has been used in place of cyclosporine. Therapy with polyclonal antilymphocyte preparations or anti-OKT3 monoclonal antibodies (Orthoclone) should be reserved for patients with delayed graft function and for the treatment of acute rejection. The routine use of these agents as prophylactic therapy is not recommended. Data on the impact of renal insufficiency on patient and allograft outcome are inconsistent. Nonetheless, the authors' literature review suggests that renal failure associated with sepsis and, except for patients with HRS, renal failure requiring dialysis are the most consistent features associated with a worse outcome. The need for preoperative or postoperative dialysis has no adverse effect on survival in patients with HRS. On long-term follow-up, despite a greater percentage of patients reaching ESRD in patients with HRS compared with their non-HRS counterparts, the overall outcome in patients with HRS following OLT is favorable. In patients with HRS requiring prolonged dialysis (i.e., greater than 4 weeks), however, irreversible renal failure may develop, necessitating CLKT. Ideally, timely referral of patients for OLT may avoid this complication and obviate the need for double organ transplantation.