Alfalfa leafcutting bees, Megachile rotundata, are used extensively to pollinate alfalfa for commercial seed production. More than 40,000 bees per acre are typically released for pollination in U.S. alfalfa fields. Although U.S. alfalfa seed production is quite succesful, the ability to sustain viable commercial leafcutting bee populations in the U.S. is not. Our study, performed over three years, looked at the reproductive success of alfalfa leafcutting bees released into large field cages at various bee densities (5,000-40,000 bees/acre). Results show that high numbers of foraging bees cannot be sustained and can never reach maximum establishment potential when contained in field cages. Over the next three years, on-going research in three small, open fields (1.5-6 acres) will examine the reproductive success of leafcutting bees, as well as alfalfa seed production, using high, medium and low bee densities.