To investigate the acid-base abnormalities of the patients with hyperlactatemia and explore the relationship of hyperlactatemia and metabolic acidosis so as to seek a more precise index of reflecting organ perfusion.From August 2009 to April 2010, all consecutive patients admitted into intensive care unit received an analysis of blood gas. Those individuals with arterial lactate ≥ 2 mmol/L were selected.In the group of hyperlactatemic patients, the occurrence of metabolic acidosis as judged by the traditional method was less than that by the Stewart's method (33.9% vs 56.0%). No typical acidemia was found. And all components of metabolic acidosis were calculated. Lactate and SIG (strong ion gap) contributed a certain percentage to metabolic acidosis in the survivor and nonsurvivor groups [(33.6 ± 17.9)% vs (28.6 ± 23.5)%, (42.1 ± 18.5)% vs (44.9 ± 23.0)%].Among the hyperlactatemic patients (Lac ≥ 2), lactate and unmeasured anions account for most instances of acidosis. These two indicators may offer a more accurate reflection of tissue perfusion.