Dead-end elimination (DEE) is a powerful theorem for selecting optimal protein side-chain orientations from a large set of discrete conformations. The present work describes a new approach to dead-end elimination that effectively splits conformational space into partitions to more efficiently eliminate dead-ending rotamers. Split DEE makes it possible to complete protein design calculations that were previously intractable due to the combinatorial explosion of intermediate conformations generated during the convergence process. c © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 999–1009, 2000