The incidence of workers' compensation claims due to heat and cold exposure was examined with regard to providing safety professionals, OSHA, and NIOSH with objective data for risk assessment. The primary data source for the study was the Bureau of Labor Statistics' Supplementary Data System, and the data file for each claim included the nature of the injury, the type of exposure, the source of the injury or illness, and the date of occurrence. Industries with more than 2 percent of the workers' compensation claims in 1979 for heat disorders included: primary metal industries; justice, public order, and safety; construction; general government; agricultural production; food and kindred products; educational services; electric, gas, and sanitary services; motor freight transportation and warehousing; amusement and recreational services; chemicals and allied products; business services; and agricultural services. Most of the heat related claims were for heat stroke and heat exhaustion. The industries with more than 2 percent of workers' compensation claims in 1979 for cold injuries were: electric, gas, and sanitary services; justice, public order, and safety; food and kindred products; construction; motor freight transportation and warehousing; general government; lumber and wood products; oil and gas extraction; business services; wholesale trade; educational services; and automotive repair and dealers and service stations. More than 75 percent of the cold related claims involved frostbite of the extremities. The author recommends that safety personnel use these data together with their knowledge of conditions and experiences of their organization to identify high risk workers.