Cystatin C has emerged as a possible, usable surrogate marker of renal function. We present a case that illustrates the clinical utility of cystatin C in the setting of acute kidney injury secondary to rhabdomyolysis. An African American male whose baseline cystatin C and serum creatinine levels taken a month prior to admission were compared against their daily values during his admission and at follow up. On admission, the patient's reduction in glomerular filtration rate (GFR) from baseline was much less when calculated with cystatin C than with serum creatinine. His clinical recovery was more reflective of the higher GFR with cystatin C than what would be assumed with his serum creatinine, which at its worst was 5 ml/min/1.73 m(2). The patient was eventually discharged from the hospital with a GFR of 40 ml/min by cystatin C despite his GFR by the MDRD equation being 12. Cystatin C may be a more accurate marker of the both the amount of injury and the rate of resolution of acute kidney injury than serum creatinine in rhabdomyolysis.