A polymorphism in the leptin gene is associated with fat deposition. Since fed cattle are often priced on a grid that considers yield and quality grades, fat deposition is an important factor in profitability. Using data from 590 crossbred steers and heifers, we simulate carcass traits to various days-on-feed and compute the associated profit under three price grids. Results indicate that leptin genotype does affect value by as much as $48 per head but has little impact on days-on-feed. Given current commercial testing fees of $40-$50 per sample, genotyping of feeder cattle appears to break even at best.