Linezolid is an oxazolidinone antibiotic used to treat a variety of gram-positive infections, including those due to methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci, as well as nocardia species. It has been reported to increase the risk of lactic acidosis and peripheral neuropathy because it disrupts mitochondrial function. Lactic acidosis usually develops after prolong use of linezolid. Here we report a case of 65 year old female who developed severe lactic acidosis within 5 days of linezolid treatment.