The specific etiological factors of coal workers' pneumoconiosis have not yet been fully understood. The prevention of this occupational disease depends upon elimination or suppression of airborne dust to which miners are exposed. The Canada Centre for Mineral and Energy Technology's (CANMET) research on respirable dust in underground coal mines emphasizes the identification and control of dust sources and the investigation of the mineralogical composition of the airborne dust. As part of the Centre's ongoing research program, measurements of respirable dust concentrations were made by using various personal samplers and portable sampling systems in two underground coal mines. The relationships between concentrations measured by different samplers and those determined by Casella Gravimetric Samplers (CGS) Type 113A are described. Dust concentrations determined by personal samplers consisting of DuPont constant flow pumps (Model P-2500A) fitted with Casella cyclones approached that determined by the CGS. Personal samplers consisting of MSA Fixt-Flo pumps (Model I) fitted with Dorr-Oliver nylon cyclones measured respirable concentration values on an average at 46% for the one mine and 58% for the other mine of the values determined by the CGS. The end-of-shift average respirable dust concentrations determined by a SIMSLIN II light-scattering system were lower than those measured by the CGS (with an average ratio 0.58 for the one mine and 0.81 for the other mine), while concentrations determined by weighing the filters used in the SIMSLIN II were higher than those measured by the CGS (with an average ratio 1.16 for the one mine and 1.19 for the other mine). Two Anderson Eight-Stage Marple Personal Cascade Impactors which evaluated respirable dust concentrations and respirable fractions of coal mine dust were also used and preliminary results show that the respirable dust concentration ratio of the cascade impactor to the CGS varies from 0.69 to 1.03. Precision and practical aspects of coal mine dust measurement by using personal samplers and other sampling systems are discussed.