Aim. Serum cystatin C (SCysC) has been proposed as a better marker of glomerular filtration rate (GFR) than serum creatinine (Scr). However, few data are available in renal transplant patients, especially, during the early postoperative phase. Methods. Thirty-nine renal transplant patients (22 men/17 women) were recruited for determination of SCysC and Scr before operation, at 1 week and at 4 weeks after operation. SCysC was determined by particle-enhanced turbidimetric immunoassay. Creatinine clearance (Ccr) was calculated using the Cockcroft-Gault formula. Results. SCysC and Scr levels significantly decreased with the recovery of allograft function. SCysC showed a significant correlation with Scr and Ccr. The relationship between SCysC and Scr showed a positive correlation (r=.849 preoperation, and r=.940 postoperation). The relationship between SCysC and Ccr revealed a negative correlation (r=.857 preoperation, and r=.876 postoperation). At the Ccr level of 50 to 80mL/min/1.73m2, the correlation between SCysC and Ccr (r=.778) was significantly better than that between Scr and Ccr (r=.553; P=.032). The concentration of SCysC was not affected by age, gender, height, body weight, hemoglobin, serum protein, glucose, or mycophenolate mofetil or azathioprine dosage. However, corticosteroids slightly increased the level of SCysC and cyclosporine (CsA) decreased it. The area under the curve of the receiver operating characteristic curve for SCysC and Scr are 0.964 and 0.915, respectively (P<.05). Conclusion. Although the concentration may be slightly influenced by prednisolone and CsA, SCysC is more sensitive than Scr to detect early and moderate deterioration of GFR in adult renal transplant recipients.