A program is given for the detection and assessment of airborne asbestos and other rock fibers in mines. An interpretation of the results and the difficulties of applying asbestos industry workplace standards are discussed briefly. The major problems are the assessment of fibers when present as a low proportion of the total particles, and the lack of knowledge of the degree of hazard of fibers of different lengths and diameters, which leads to difficulty in comparing these fiber concentrations with those of standards developed mainly in asbestos textile workplaces.