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their prey selection, in a meadow reach of a subalpine stream (3,205 m above mean sea level) in the Central Rocky Mountains. Understanding of the diet and factors affecting diet composition of brook trout in mountain streams may yield insight into the factors governing the abundance and growth of stocks in subalpine systems. Our objectives were: 1) to describe the diet of two size classes C~. 150 mm total length (TL) and > 150 mm) of brook trout during the open water period, 2) to describe the composition of the macroinvertebrate drift during the same period, and 3} to assess the selectivity of brook trout for prey organisms in the drift. METHODS Telephone Creek, Albany County, Wyoming is a high-elevation stream on the Snowy Range in the Medicine Bow National Forest. The stream originates in the alpine zone at 3,350 m above mean sea level. The study reach was at an elevation of 3,205 m in a meadow area (stream channel gradient = 0.4%). At the stu~y reach, Telephone Creek is a second order stream with a drainage basin of 3.9 k~ . Average daily discharge through the study reach ranged from 0.011-0.78 m Is between 1969 and 1984 (Chisholm 1985). Dissolved oxygen remains near saturation throughout the year, while dissolved solids are low (total alkalinity = 24 mgll -as CaC03)' The study reach was 90 m long, with a mean wetted width of 2.1 m, mean depth of 16 cm, and pools up to 30 cm deep during base flow in September 1985. The banks were vegetated with willows (Salix spp.), sedges (Carex spp.) arrd grasses. Undercut banks of > 10 cm width occurred over 57% of the reach. Substrate was dominated by fine gravel (0.25-3.4 mm diameter) in both riffles and pools. Brook trout were the only salmonids in the study reach. The reach had a high biomass of brook trout, 318 kglha in 1984 (Chisholm 1985), but the fish grow slowly, reaching approximately 200 mm in four years, with little growth beyond that 1 ength. Longnose sucker (Catostomus catostomus) were observed withi n the study reach in 1984, but they were not observed in our 1985 electrofishing samples. Brook trout and macroinvertebrate drift were sampled on three occasions in July, August and September. Trout were collected by electrofishing between 0700 and 1200 hrs on each sampl ing occasion. The fish were measured to the nearest millimeter, the digestive tracts were excised and the stomachs were preserved in 10% formalin. Drift samples provided an estimate of prey abundance. Drift samples were collected at three consecutive 6 hr intervals between 1800 and 1200 hrs us i ng three nets; 363 mi cron open i ng, nylon mesh with a 45 cm wi dth. The nets were set so the openi ngs extended above the water surface and occupi ed approximately 75% of the wetted width of the study reach. Stomach contents and drift samples were sorted, i dent ifi ed and enumerated in the 1 aboratory under a dissecting microscope. Selectivity was computed using the linear food selection index of Strauss (1979). .0: 12