The U.S. Bureau of Mines in 1986 conducted a probability sample survey to measure the characteristics of the U.S. mining industry workforce. This paper discusses the importance of collecting demographics data for the purposes of analyzing existing injury and illness data. In particular, it shows how demographics survey data are utilized in identifying subpopulations of the 1986 mining workforce (by sex, age, experience at present job, and job title or occupation) that exhibited a disproportionately higher- or lower- than-average number of work-related back injuries, as well as lost workdays due to back injuries. These injuries in 1986 accounted for 19 pct of all mining incidents and 29 pct of all lost workdays. The results of the analysis show that of all the subpopulations studied, continuous miner and related machinery operators in the coal industry had the highest risk for back injuries and related lost workdays, about four times the average. For both coal and metal and nonmetal sectors (metal, stone, sand and gravel, and nonmetal), the workers in the age group 30 to 39 were at a higher than average risk, whereas those age 50 and over were the least prone (below average) to back injury problems.