Mounds of the western pebble-mound mouse, Pseudomys chapmani, are found throughout the species' Pilbara range in areas with iron-ore deposits of economic significance. Translocation techniques are being examined as a means of minimising the impact of mining on this species. In the absence of detailed information on the biology of P. chapmani, translocation is inadvisable. To provide such basic information, animal densities, mound demographics and population sizes, and home-range end core-area sizes were obtained by a combination of trapping and radio-tracking. Mounds of P. chapmani were found to be inhabited by social groups of up to 12 animals. Estimates of home-range size gave mean (+/- s.e.) values of 14.4 +/- 6.7 ha and 4.6 +/- 2.7 ha for males and females, respectively; core areas were recorded at 0.93 +/- 0.29 ha sor males and 0.29 +/- 0.16 ha for females. Considerable overlap of home ranges was recorded between individuals from the same and different mounds. Overlap at the core-area level occurred only between individuals from the same mound. The high level of social complexity and mound fidelity indicates that translocations should be directed at the level of the social group rather than at the level of the individual.