We employed a spatially explicit simulation model to assess growth rate potential for lake trout (Salvelinus namaycush) in Flaming Gorge Reservoir, Utah-Wyoming. Late-summer water temperatures and forage fish densities in 168 habitat cells were collected from 1989 to 1996 and were used to estimate the potential growth of lake trout inhabiting each cell. Results of model simulations indicated that habitat quality for lake trout growth had decreased from 1990 to 1993. This decrease in lake trout growth rate potential was related to decreased forage fish densities during this period. Lake trout condition, as measured using length-weight analyses of individuals captured in spring gillnetting surveys, also decreased from the early 1990s to the mid-1990s. The change in the slope of the length-weight relationship was correlated with the proportion of habitat cells containing positive simulated growth rate potentials (r2 = 0.60, p = 0.024). No significant correlation between the sum of growth rate potentials in habitat cells and changes in the slope of the length-weight relationship was apparent. These correlations suggest that spatially explicit models of habitat quality have relevance to the performance of individual organisms functioning in field environments.