One of the major challenges in transplantation over the past two decades has been managing long-term renal function. Serum creatinine is the most commonly used serum marker of renal function. However serum creatinine is insensitive for detecting small decreases in glomerular filtration rate (GFR). Another marker for renal function is cystatin C. Dharnidharka et al concluded that cystatin C is superior to serum creatinine as a marker of kidney function since cystatin C was a more sensitive marker than serum creatinine for detecting decreases in GFR. Pirsch et al reported that tacrolimus-treated patients had a lower incidence of severe acute rejection and better lipid profiles than cyclosporine-treated patients.