This report summarizes the phytoplankton communities of 35 Canadian Shield lakes located within the Experimental Lakes Area (ELA) near Kenora, Ontario. The lakes are representative of the area and the phytoplankton communities are probably comparable to those in other Canadian Shield lakes. On the basis of size the lakes were grouped into three classes. Four lakes representing the three classes were chosen for detailed analysis of seasonal variations in phytoplankton biomass and species composition.