The present invention relates to compositions and methods for treating orthostatic intolerance in a subject in need thereof. Methods involve, e.g., administering an amount of a norepinephrine precursor, whereby said amount is effective for treating orthostatic intolerance. A useful norepinephrine precursor is threo-3-(3,4-dihydroxyphenyl) serine (L-threo-DOPS), a derivative thereof, or a pharmaceutically-acceptable salt thereof.