The objective was to evaluate the correlation between some metabolic parameters and efficiency measures in water buffaloes of three genetic groups finished in feedlot. Seventy-five non-castrated males from three genetic groups Murrah, Mediterranean and Jafarabadi (25 animals/breed) with initial BW and age means of approximately 314 ± 117 kg and 390 ± 58 days were used. The efficiency measures (Residual feed intake - RFI; Residual body weight gain - RG; Residual feed intake and body weight gain - RIG; Gain to feed ratio - G:F; and, Feed to gain ratio - F:G) were calculated considering the metabolic BW, DMI, and ADG obtained during 84 days of feeding. The carcass dressing percentage obtained after slaughter was used to calculate the biological efficiency (BEff; carcass gain per kilogram of DMI) during the same period (84d). Blood samples were collected at the beginning and at the end of the experiment for determination of total protein, albumin, urea, creatinine, cholesterol, triglycerides, high density lipoprotein (HDL), very low density lipoprotein (VLDL), low density lipoprotein (LDL), glutamic oxalacetic transaminase (GOT), gamma-glutamyltransferase (GGT), alkaline phosphatase (AF), total bilirubin, and glucose. The glucose was determined by colorimetric and all the other parameters by kinetic method, using commercial kits (Bioclin, MG, Brazil) in an automatic analyzer model BS-200 (Mindray Bio-Medical Electronics Co., China). The data were analyzed by the CORR procedure of SAS with the use of the PARTIAL command to control the breed effect and day of collection. Significance was considered if P<0.05 and tendencies if P<0.10. No correlations (P>0.05) were detected among the parameters urea, creatinine, cholesterol, triglycerides, HDL, VLDL, LDL, GOT, bilirubin, and glucose with efficiency measures. The correlations (P≤0.05) and tendencies (P≤0.10) are showed in Table 1. In conclusion, some blood serum parameters can be correlated with efficiency measures of water buffaloes finished in feedlot.