The results of field surveys conducted under the National Occupational Health Survey of Mining (NOHSM) program were summarized. NOHSM was a series of surveys conducted by NIOSH to characterize potential exposures that could affect worker health (health related agents) at US mines. A representative sample of 491 US mines which extracted 66 different mineral commodities were surveyed from May 1984 through August 1989. The 491 mines included 431 metal and nonmetal mines and 60 coal mines and employed 59,734 workers. Each NOHSM survey consisted of three phases: a questionnaire, chemical inventory, and a worksite visit. The questionnaire sought information on medical services offered at the mine, industrial hygiene practices, and general information about the mine such as industrial classification, commodities mined or processed, and the size of the workforce. The chemical inventory collected information on all chemical substances and brand name products present. The worksite survey observed and interviewed workers to assess their potential exposures to physical agents such as noise, heat, or radiation, factors leading to musculoskeletal overloading, to welding or soldering fumes, to chemical substances, and to bulk mineral dusts. Altogether, 84,939 brand name products and 2,570 chemical substances were found at the mines. From 13 to 73% of the workers were potentially exposed to physical agents. Noise was the most prevalent exposure. From 18 to 39% of the workers were potentially exposed to factors causing musculoskeletal overload. Musculoskeletal overloading of the neck or back was the most prevalent potential exposure. Thirty two percent of the workers were potentially exposed to welding agents or cutting processes. Most of the chemical substances and brand name products were used as fuels and in maintenance. Of the bulk dust samples, 505 contained at least 5% quartz (14808607) and 38% contained more than 10% quartz. Arsenic (7440382) was found in 0.17 to 0.93% of the samples. Chrysotile (12001295) and other asbestiform minerals were found in 1.0 to 35.0% of the dust samples.