Reactor physics calculations were performed with ENDF/B Version-Ill cross-section data for several of the fast-reactor data-testing assemblies specified by the Cross Section Evaluation Working Group. In these calculations, multigroup cross sections were generated using both the Argonne MC2 and SDX codes for comparative purposes. The multigroup cross sections were then used in Sn transport-theory calculations to obtain keff and central activation ratios, and in perturbation-theory calculations to obtain central worths. Results with MC2 and SDX cross sections are in good agreement except when regions containing large amounts of a structure material are involved.