The species compositions and densities of the littoral and pelagic zooplankton assemblages in Crater Lake were compared. The littoral and pelagic zooplankton assemblages of most lakes are typically different due to different habitat conditions in the two zones. The littoral zone of Crater Lake lacks many of the habitat characteristics, which distinguish a typical littoral zone from the pelagic zone. In fact, none of the water quality variables measured differed significantly between the littoral zone and epilimnion of the pelagic zone in Crater Lake. The littoral and pelagic zones of Crater Lake were sampled with twelve paired sites in August and again in September of 1995. For the purposes of this study, the littoral zone was defined as lakeward from the shoreline to the 10m depth contour. At each paired site the pelagic assemblage was sampled to a depth of 120m at the 200m depth contour. Despite the almost identical water quality between the pelagic and littoral zones of Crater Lake, lack of vascular macrophytes in the littoral zone, and well-mixed epilimnion, the littoral zooplankton assemblage differed from the pelagic assemblage in both species composition and density. Several ubiquitous zooplankton taxa dominated both the littoral and pelagic zooplankton assemblages, although the density of these taxa as well as the relative abundance of these taxa differed between zones. These ubiquitous species reached their maximum densities in the metalimnion of the pelagic zone at a depth range of 10 to 60 meters below the lake surface and were considered primarily pelagic. A shift in wind direction between sampling periods influenced the distribution of pelagic zooplankton taxa in the littoral zone. Twenty-four taxa were recorded in the littoral zone, and aside from infrequent exceptions, none of these taxa were found in the pelagic zooplankton assemblage. Most of the littoral taxa were primarily adapted to the benthic zone. / Graduation date: 1999