Abstract: The mechanism of inactivation of monoamine oxidase (MAO) by 5-(aminomethyl)-3- aryl-2-oxazolidinones has been investigated.(R)-and (S)-3-[4-[(3-chlorophenyl) methoxy] phenyl]-5~[(methylamino) methyl]-2-oxazolidinone (1) exhibit all of the properties of a mechanism-based inactivator. Several other analogues of 1 also inactivate MAO. Inactivation of