The monoamine oxidases (MAO-A and MAO-B) are flavoenzymes located in the outer mitochondrial membrane responsible for the oxidative deamination of many endogenous and exogenous monoamines. Recognition of the importance of monoamine oxidases as targets for drug intervention for the treatment of a variety of conditions, such as schizophrenia, Alzheimer's disease, Parkinson's disease and other psychiatric and neurological disorders, has produced an enormous interest in the development of molecules that act as inhibitors on these enzymes. This review mainly focuses on the numerous monoamine oxidase inhibitor (MAO-I)-related patents published from August 2002 to June 2005. In this paper recent developments of monoamine oxidase inhibitors are reported, ordering all patents by molecular structure. A structure-activity relationship (SAR) study that reports on known MAO inhibitors is also outlined before a discussion on new associations with other drugs of classical MAO inhibitors and their new target.