Optimal sizes, number, and locations of Tennessee livestock auction markets were identified as those which minimize the combined costs of assembling and marketing livestock for the state using a separable programming model. The model includes transportation costs, economies of size in market operation, a proxy for reductions in buyers' operating costs attributable to increasing market volumes, and livestock production density, both in and around the state. The model is sufficiently comprehensive and descriptive to be of practical use by policy makers who influence industry change. Results indicate that a reduction in market numbers would lower combined costs.