The guide summarizes the present state of technology. It presents and interprets the data on lightweight aggregate concretes from many laboratory studies, accumulated experience resulting from successful use, and the performance of structural lightweight aggregate concrete in service. The guide is intended for all sections of ACI readership. It includes a definition of lightweight aggregate concrete for structural purposes and it discusses in condensed fashion the production methods for and inherent properties of structural lightweight aggregates. Other chapters follow on current practices for proportioning, mixing, transporting, and placing; properties of hardened concretes; and the design of structural concrete with special reference to ACI 318.