Ordered intermetallic compounds based on aluminides and silicides constitute a unique class of metallic materials that have promising physical and mechanical properties for structural applications at elevated temperatures. This Article provides useful information on mechanical and metallurgical properties, material processing and fabrication, structural applications, mechanical behavior, environmental embrittlement, alloying effects, and crystal structure of aluminides of nickel, iron, titanium, and silicides. It describes the cleavage and intergranular fracture in trialuminides.