This article discusses the effect of alloying on high-strength low-alloy (HSLA) steels. It explains where HSLA steels fit in the continuum of commercial steels and describes the six general categories into which they are divided. It provides composition data for standard types or grades of HSLA steel along with information on available mill forms, key characteristics, and intended uses. The article explains how small amounts of alloying elements, particularly vanadium, niobium, and titanium, control not only the properties of HSLA steels, but also their manufacturability.