As water resources become limited, the selection of turfgrasses with high water use efficiency becomes more and more important. Selecting turfgrass cultivars with low carbon isotope discrimination (Δ) has shown potential for identifying cultivars with reduced evapotranspiration (ET). An objective of this work was to determine the relationship between Δ and water use efficiency (WUE) in cultivars of tall fescue (Festuca arundinacea Schreb.) maintained as turfgrass. A second, related objective was to determine the relationship between Δ and WUE for the types of tall fescue grown (forage, standard, semi-dwarf, and dwarf). Water use efficiency of 12 cultivars of tall fescue was evaluated in lysimeters (20-cm-diam., 75-cm-length) filled with a mixture of sand, soil and peat over six 3-d harvest periods. Clipping dry weight accumulated above a 50-mm base mowing height for each 3-d harvest period was determined and used in conjunction with gravimetric water loss to calculate WUE. Differences among cultivar and group Δ and group color were observed, depending on the harvest period. The practical applicability of using Δ to determine the water use efficiency of turfgrasses should be further explored, particularly in a field research setting.