Technical Abstract: Heat stress in feedlot cattle is a common summer time occurrence in cattle-producing parts of the world (United States, Australia, Brazil, etc.). The impact of heat stress on feedlot animals is quite varied--from little to no effect in a brief exposure, to causing reductions in feed intake, growth, and well-being of the cattle in a moderate event, to death of vulnerable animals during an extreme event. The level of heat stress an animal experiences can be broken down into three primary factors: animal susceptibility, environmental conditions, and management strategies. Each of these factors can also be broken down into different elements. This paper describes the physical and physiological processes that describe homeostasis along with the factors affecting animal susceptibility, methods of summarizing environmental conditions, and management strategies that can be used to relieve stress.