Using minirhizotrons, fine root dynamics were compared in two Atlantic white-cedar swamps with contrasting hydroperiods (intermittently and persistently flooded) in order to evaluate the effects of flooding regime on fine root depth, abundance, production, and longevity. Despite the higher mean water-table depth in the persistently flooded site, no differences in rooting depth were observed. Root length density, root abundance, and root longevity were generally greater in the persistently flooded site throughout the 439-day study period, although root length production was similar between the two sites. These results suggest that prolonged inundation in Atlantic white-cedar swamps decreases root elongation rates, but due to greater observed root densities, stand-level belowground production remains similar to that of intermittently flooded stands. Significant increases in root mortality were observed in the intermittently flooded site during a period of water-table drawdown, suggesting less than optimal hydrologic conditions at this site.