Linezolid, a novel antimicrobial with activity against gram-positive bacteria including pathogens resistant to traditional antimicrobials, also inhibits monoamine oxidase. This latter property can cause potentially lethal adverse interactions with antidepressant medications. Long known to psychiatrists, monoamine oxidase inhibitors (MAOIs) and complications of their use may be unfamiliar to medical and surgical practitioners who may thus unwittingly precipitate a hypertensive crisis or serotonin syndrome. We review the pharmacology of MAOis and describe 3 clinical situations In which linezolid-selective serotonin inhibitor (SSRI) interactions, actual or potential, figured prominently.