Technical Abstract: Yields of crops can be reduced due to predation by herbivores. Field grown Navy Bean (Phaseolus vulgaris L.) is susceptible to damage by deer. Seed of the Navy Bean cv. Aspen were sown in a sandy loam soil in May 2006. When plants reached the first trifoliate leaf stage exclusion cages were set around six-foot randomly chosen stretches in rows in six locations in the field. Six-foot sections of rows immediately adjacent to cages were left unprotected. During the growing season deer tracks and nipped off tips of plants were found in the field. When 80% of leaves had dropped plants in the protected and unprotected portions of rows were harvested. Seed were collected and potential yields estimated and compared. Yields from protected plants were 20% greater than from unprotected plants. Although physically protecting plants improved yield, the potential yield was below that which would return a profit for the producer. It is likely that environmental conditions in the southern Great Plains are incompatible with Navy Bean production.