OverviewEditor's Note: A hypertext-enhanced version of this article can be found on the TMS web site at http://www.tms.org/ pubs/journals/JOM/9711/Ejiofor-9711.html.In the past ten years, materials R&D has shifted from monolithic to composite materials, adjusting to the global need for reduced weight, low cost, quality, and high performance in structural materials. This article reviews developments in the molten processing of particulate Al-Si alloy composites and their respective properties. Existing and emerging processing innovations are discussed, and the reinforcement phases in prominent R&D activities are identified. The vortex (or mixing) method continues to be the most popular processing method in use because of its ease of operation, total production cost, and suitability, while the infiltration, compocasting (or rheocasting), in-situ, and spray atomization and codeposition techniques receive less attention.