Diamondback terrapin (Malaclemys terrapin) population dynamics in North Inlet–Winyah Bay, South Carolina, a relatively undeveloped salt marsh estuary, were determined from 6 yrs of mark–recapture data. Total terrapin abundance in 4 adjacent creeks was estimated annually at 260–360 terrapins (144–200 terrapins/km) and the mean annual survival probability for terrapins was 0.78. This study in a protected terrapin habitat will provide data for population models and comparisons with threatened populations.