Distinct differences in the phytoplankton composition at upstream and downstream stations were documented for the Duplin River, Georgia. A phytoflagellate and cyanobacterial flora predominated the upstream station. Downstream diatoms and cyanobacteria were dominant. At the downstream station a winter-spring bloom was dominated by Asterionella glacialis Castracane and Skeletonema costatum (Grev.) CL., with the latter species also abundant in the autumn. The seasonal occurrence and general abundance of the 177 taxa recorded are presented. The general composition of the algal flora is similar to that previously reported for the southeastern continental shelf.