This report identifies, describes, and quantifies the cost effects of structural materials that are likely to be incorporated into aircraft becoming operational in the 1990s (aluminum, aluminum-lithium, steel, titanium, graphite/epoxy, graphite/bismaleimide, and graphite/thermoplastic). The authors present a primer for advanced aircraft structural materials emphasizing polymer matrix composites. They then present both cost data and a cost estimating methodology sensitive to material mix. For each material type, they present separate cost factors for two time frames (the late 1980s and the mid-1990s) and for the following cost elements: nonrecurring engineering, nonrecurring tooling, recurring engineering, recurring tooling, manufacturing labor, manufacturing material, and quality assurance. Although composites offer advantages, including reduced weight, reduced number of fasteners, increased corrosion resistance, reduced radar cross-section, and the potential for extended life, the cost data show that composite materials are more expensive than aluminum on a cost-per-pound basis.