We report a case of life-threatening lactic acidosis in a 10-year-old male with HIV stage B2 infection, presumed to be vertically acquired. This occurred after several months of therapy with d4t, ddl, and nevirapine. His most recent CD4 count was 347 cells per microliter and viral load 16,000 copies per milliliter 3 weeks prior to admission. The peak lactic acid level was 12.4 mmol/L. Although multiple therapeutic interventions took place, the patient showed rapid improvement and resolution temporally associated with the administration of levocarnitine.