Serum creatinine is the most widely use parameter to assessing renal function, even though limitations, some time is necessary measure 24 h creatinine clearance (CLcr), or estimate Cockroft-Gault (C-G) or MDRD formulas. Different methods can offer different results, and cause confusion in clinicians. Using Cystatin-C as new parameter of renal function could suppose an important improvement. The objective of our study was to compare the different methods from renal evaluation and establish the utility of cistatina-C in the hospital area. In the study were included 70 patients (44 men) selected of random way, predominate patients with kidney disease and diabetics, which was made CLcr and calculated C-G and MDRD formulas. The mean age of the patients was 66+/-14 years, mean weight 73+/-17 Kg, creatinine 2,14+/-1,77 mg/dL, cystatin-c 1,77+/-1,18 mg/L, CLcr 54,39+/-36,2 mL/min. The correlation of 1/Crea with the Clcr, C-G and MDRD formulas was respectively: 0,7735, 0.8269 and 0.9613, (p< 0.0001). The correlation of 1/Cist with the Clcr, C-G and MDRD was respectively: 0,836, 0.8142 and 0.832, (p<0,0001). By Bland-Altman graphs the average of the difference between CLcr with CG and MDRD was 2,8 mL/min and -1,5 mL/min respectively. Comparing CG with MDRD was 1,7 mL/min. The average of the observed absolute differences between CLcr with CG and MDRD was 13.5 mL/min and 17.1 mL/min respectively. Between this formulas the average was 12.5 mL/min. Statistically significant differences between the different methods from renal evaluation do not exist (p>0,05). In conclusion, most of the urine collections could be avoided with the use of the formulas. Cystatin-c is far beyond the creatinine, mainly to detect slight renal alteration (sensitivity 80,4% U.S. 44,7% in men) becoming a promising alternative, that could reduce considerably hidden renal insufficiency (non detected by creatinine), although more studies are needed to confirm.