The Blanket Comparison and Selection Study (BCSS) had as its primary goal the selection of a limited number of blanket concepts for fusion power reactors, to serve as the focus for the U.S. Department of Energy blanket research and development program. To help provide a common basis for evaluation of all candidate blanket concepts considered by the BCSS, a structural materials data base assessment was performed that included a compilation of available materials properties data, specification of limiting criteria for materials performance, and determination of design allowable parameters. Three classes of alloys are currently considered as leading candidates for the first-wall/blanket structure of a fusion power reactor. For the BCSS, one reference or baseline alloy was selected from each class and one low-activation counterpart to each reference alloy was identified for evaluation. The alloy classes, reference alloys, and low-activation analogs selected were: austenitic stainless steels (primary candidate alloy; manganese-stabilized steel); ferritic or martensitic steels (HT-9, Fe-11 Cr-2.5 W-0.3 V-0.15 C); and vanadium-base alloys (V-15 Cr-5 Ti, reference alloy is low activation). The critical nuclear, thermophysical, and mechanical properties of the three reference alloys were reviewed. Where insufficient data exist for a reliable assessment, best estimates were provided for use in the blanket concepts development. For the low-activation analogs, the same properties as their respective reference alloys were assumed, including radiation damage resistance. The design stress limits, maximum allowable operating temperature, and lifetime were set primarily by radiation damage considerations. Critical design issues associated with each of the reference alloys and low-activation analogs were identified, together with limiting criteria for materials performance.