Samples of phytoplankton were collected by a van Dorn sampler in 1972 and samples of zooplankton by a Wisconsin style net in 1971 and 1972 from Alexie, Baptiste, Chitty and Drygeese lakes near Yellowknife,Northwest Territories. Seventy-nine major taxa of phytoplankton were identified, Chitty Lake having the most taxa (56) and Alexie Lake the fewest (28). Chrysophyceae dominated the phytoplankton in all four lakes while Cyanophyceae or Cryptophyceae were second in importance. Seasonal changes in numbers and biomass were not consistent among the lakes. Most differences in plankton populations observed among the lakes reflected the fact that they are located on two separate sub drainages of the Yellowknife River system.