This article describes the process of materials selection in relation to design process, such as materials selection for a new design and materials substitution for an existing design. It reviews the performance characteristics of materials using prototype tests or field tests to determine their performance under actual service conditions. The article describes the selection of a material in relation to a manufacturing process and presents the factors that influence materials selection based on costs and related aspects. The factors include metallurgical requirements, dimensions, processing, quantity, packing, marking, and loading. The article discusses how the needs for materials data evolve as a design, such as conceptual design, embodiment design, and detail design. It describes the methods of materials selection, namely, cost per unit property method, weighted property index method, and limits on properties method.