Background and Aims. Metabolic acidosis (MA) is a frequent and serious complication in HIV-infected patients. The aim of the study is to compare patients with and without MA associated with HIV. Methods. Patients were retrospectively studied involving all HIV-infected patients with blood gas analysis performed during hospital stay admitted to a single hospital between April 2004 and July 2006. Statistical analysis was performed using SPSS 10.0 for Windows. Results. Included in the study were 159 HIV patients, 72 cases (45.3%) with MA and 87 cases (54.7%) without. The comparison of both groups showed a mean arterial pH of 7.24 +/- 0.08 vs. 7.44 +/- 0.05, HCO3 12 +/- 5.7 vs. 21 +/- 5.1 mEq/L, serum urea 81 +/- 68 mg/dL vs. 39 +/- 46 mg/dL and serum creatinine 2.7 +/- 2.6 mg/dL vs. 1.2 +/- 1.9 mg/dL in MA-HIV and non-MA-HIV, respectively (p <0.05). Antiretroviral therapy (ART) was being administered to 38 subjects (52.8%) in MA-HIV group and 45 (51.7%) in non-MA-HIV group (p = 0.57). There was no association between the use of ART and MA. Mortality was higher in patients with acidosis (52.7 vs. 17.2%, p <0.0001). Conclusions. In the present study, MA was associated with acute kidney injury and increased mortality. There was no association between the use of ART and MA. (c) 2009 IMSS. Published by Elsevier Inc.