The James River and the Chesapeake Bay meet in the waters of Hampton Roads, Virginia. A study was made of the phytoplankton in Hampton Roads and adjoining Willoughby Bay from January 1964 to May 1965. The composition and seasonal variations of total phytoplankton and, major species are described for three stations in this area. The major phytoplankters were neritic north temperate species. The diatoms, chieflySkeletonema costatum, Asterionella japonica, andNitzschia pungens atlantica, composed the winter and early spring maxima. Diatoms and large numbers of phytoflagellates were the major constituents in collections during summer and fall. The fluctuation in the composition and vertical distribution of phytoplankton is discussed for a 24-hour period, at one station, in Hampton Roads, whereSkeletonema costatum was the most numerous plankter in all of the samples.