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1. Determine the types and relative abundance of benthic organisms. 2. Determine differences in the benthic population in different areas of the reservoir. 3. Determine seasonal charges in the benthic population. DESCRIPTION OF THE STUDY AREA. Flaming Gorge Reservoir, a large main-stem impoundment of the Green River has been described in detail by Eiserman and Stone. Bottom fauna samples were collected from the three major reservoir areas; canyon, open and inflow (Figure 1). METHODS Bottom samples were obtained with an Ekman dredge at the one-to- two-foot range and with a Petersen dredge at the other depths. Sampling was carried out at two stations in 1964 - one in the canyon area and one in the open area. One sample was collected from each station. Samples were collected in May, July, September and October in the canyon area and June, July, September and October in the open area. In 1965 sampling was done during the month of July. Samples were collected from two stations in the canyon area and from one each in the other two areas. Three samples were collected from each station at varying depths. Samples of the benthos were collected during the period May through October in 1966 so that monthly variations in abundance could be determined. No samples were collected during winter months. To further refine sampling in 1966, productive and unproductive habitat was designated in the open and inflow areas. Productive habitat was somewhat arbitrarily considered as having a substrate composed of vegetation, mud, sand and gravel. Substrate composed of shale, clay and silt was termed unproductive. During the 1966 sampling season, three samples were collected from the one-to-two-foot depth range and two samples each from the 10 and 25-foot depths along established stations in areas designated as produc- tive. No samples were collected at the one-to-two-foot depth range and one sample each was collected at the 10 and 25-foot levels in the un- productive habitat. Only the productive habitat was sampled in the canyon area. 32