The risk of end-stage renal failure is particularly high in patients with diffuse proliferative glomerulonephritis. Despite the diverse and complex interplay of various causative factors in individual patients, two previous studies suggested that SLE patients who experience glomerulonephritis that does not diminish following treatment with conventional immunosuppressive therapies have increased risk for subsequent deterioration of renal function and poor long-term outcome. This suggests that there is an urgent need for alternative immunosuppressive therapies for treatment of SLE, and motivated our investigation of TAC. On the other hand, it is well know that calcineurin inhibitors (such as TAC) are associated with chronic nephrotoxicity. For example, Tse et al. showed that one of six patients developed chronic nephrotoxicity after 10 months of TAC therapy. As a calcineurin inhibitor, TAC has a lower potential for nephrotoxicity than cyclosporine.