Miniature radio-transmitters were used to follow movements over a 10-day period of the 10 g honey possum Tarsipes rostratus, and the areas covered were compared with home-range estimates calculated from long-term mark-and-recapture records using pitfall traps. The study was carried out in the Scott National Park, in the extreme south-west of Western Australia, and shows that honey possums may move far greater distances than is apparent from trapping records. The overall mean area used determined by radio-tracking was significantly larger at 0.54+/-0.19 ha than the apparent home range of 0.03 0.01 ha determined by trapping. The area used by males was significantly greater than that of females when measured by radio-telemetry (0.79+/-0.24 ha vs 0.14+/-0.08 ha, P=0.058), but did not differ significantly when estimated from trapping records (0.03+/-0.01 ha vs 0.01+/-0.01 ha). These data suggest that honey possums frequent plant assemblages at night where they are vulnerable to pitfall trapping, but that males, particularly, spend the day in other areas that may be as far as 200 m distant.