The vascular flora occurring in the intertidal zone of Brent Marsh was surveyed during 1987-94. The muddy-peaty deposits that form the tidal shoreline of Brent Marsh lie in fresh to brackish waters of the Potomac River in Stafford County, Virginia. The microhabitats present in the intertidal zone of Brent Marsh were found to support a large diversity of primarily herbaceous species. One hundred twenty-one taxa are reported, of which five are endemic to the rare fresh to brackish intertidal habitat characteristic of large tidal river systems in the Chesapeake drainage.