Asbestos (1332214) exposure levels experienced by automobile mechanics using various control techniques during maintenance and replacement of drum brakes were determined. The study focused on vehicles with brake drum sizes of 12 inches or less. Five methods for controlling exposure to asbestos during brake repair were evaluated. These included two commercial enclosure devices with ventilation provided by a high efficiency particulate air (HEPA) filter equipped vacuum, a HEPA filter equipped vacuum cleaner with no enclosure, a wet brush/cycle system with recirculating cleaning solution, and an aerosol spray to wet the brake assembly. All of the five methods tested, in combination with the work practices used, controlled the exposure of the mechanics during break servicing to less than 20 percent of the NIOSH recommended exposure limit of 0.1 fiber per cubic centimeter (f/cc). The brake mechanics' exposure for 2 hour sampling periods ranged from less than 0.004f/cc to 0.016f/cc. Personal exposure were at least an order of magnitude lower than personal exposures reported in the literature. Transmission electron microscopy indicated asbestos fibers of all sizes were present. Brake service to two heavy duty trucks showed higher asbestos concentrations than servicing for smaller size vehicles. Except for the effect of drum size, differences in personal and near source sample concentrations among the vehicles evaluated were very small, and no trends with respect to mileage, model, or model year were noted. Not all control devices of a given type would be expected to be equivalent. Different controls and work practices, techniques, and drum sizes contributed to the observed test differences. Fibers in dust samples from the brake drums of 40 of the 43 vehicles tested were mostly chrysotile (12001295). The other three appeared to have nonasbestos type brake shoes.