Abstract: Methods of treating Parkinson's disease in a human by administering an effective amount of at least one monoamine oxidase (MAO) A inhibitor by a nasal, intrapulmonary or parenteral routes are disclosed. Reversible or irreversible MAO A inhibitors, or non-selective MAO inhibitors, can be used, and more than one MAO A inhibitor can be administered concurrently. The MAO A inhibitor can be administered in conjunction with other drugs, such as MAO B inhibitors.