Changes in abundance and seasonal composition of standing stocks of phytoplankton were evaluated at nine stations in 1972, 1973 and 1974. These data were compared to previously reported data from 1969 to 1971 (Michalski, 1972). Water clarity, chlorophyll and phosphorus levels were also assessed. Quantitative measurements of phytoplankton were recorded as areal standard units per millilitre. Over the period 1969-1974 there has been a small overall decrease in algal populations in the Nanticoke region with the exception of 1970 when there was a substantial increase in algal levels. The bimodal pattern of algae development described for 1969-1971, while present in 1972, was less pronounced and was not distinctly observable in 1973 and 1974. Major changes in species composition were not detected from one year to the next. However, there was a shift toward a more homogeneous representation of all algal groups with a greater representation of the chlorophycean species during the mid-summer months. While the overall picture of phytoplankton conditions at Nanticoke suggests that the area is both homogeneous and mesotrophic, continued monitoring will be important to ascertain if these conditions are altered.