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Economic losses are incurred by the US livestock industries because farm animals are raised in locations and seasons where effective temperature conditions venture outside their zone of thermal comfort. The objective of this review was to estimate economic losses sustained by major US livestock industries from heat stress. Animal classes considered were: dairy cows, dairy heifers (0 to 1 yr and 1 to 2 yr), beef cows, finishing cattle, sows, market hogs, broilers, layers, and turkeys. Economic losses considered were: 1) decreased performance (feed intake, growth, milk, eggs), 2) increased mortality, and 3) decreased reproduction. USDA and industry data were used for monthly inventories of each animal class in each of the contiguous 48 states. Daily weather data from 257 weather stations over a range of 68 to 129 yr were used to estimate mean monthly maximum and minimum temperatures, relative humidity, and their variances and covariances for each state. Animal responses were modeled from literature data using a combination of maximum temperature-humidity index, daily duration of heat stress, and a heat load index. Monte Carlo techniques were used to simulate 1000 times the weather for each month of the year, for each animal class, for each state, and for each of four intensities of heat abatement (minimum, moderate, high, and intensive). Capital and operating costs were accounted for each heat abatement intensity. Without heat abatement (minimum intensity), total losses across animal classes averaged $2.4 billion annually. Optimum heat abatement intensity reduced annual total losses to $1.7 billion. Annual losses averaged $897 million, $369 million, $299 million, and $128 million for dairy, beef, swine, and poultry industries, respectively. Across states, Texas, California, Oklahoma, Nebraska, and North Carolina accounted for $728 million of annual losses, or 43% of total national losses. Results point to a need for more energy and capital efficient heat abatement systems.