Radio-telemetry was used to investigate roosting and movement patterns of the black flying fox (Pteropus alecto) in the seasonal tropics of the Northern Territory. Sixteen P. alecto were tracked during a 12-month period to 34 roosts and were recorded at 49 foraging sites. Pteropus alecto moved roosts seasonally, from bamboo and mangrove habitats in the dry season to rainforest in the wet season. All radio-collared male and female P. alecto roosted in rainforest during the major part of the wet season. Climatic influences may be responsible for this behaviour, with rainforest perhaps providing stable temperatures and shelter from the monsoonal rains. There was a significant seasonal difference in the distances moved by females between successive roosts. There was an association between roosting and foraging habitat: P. alecto roosting in bamboo and mangroves foraged predominantly in woodland, P. alecto roosting in rainforest foraged in Melaleuca spp. and rainforest habitat. Females covered greater distances from roosts to foraging locations than did males. Distances from roosts to foraging sites were reduced for males and females during the build-up season (September to November) and wet season (December to April). Seasonally, foraging habitat shifted both floristically and spatially with no significant difference between the sexes. The movements of one female P. alecto were recorded at hourly intervals over three consecutive nights at the beginning of the wet season. Movement patterns were very similar between nights and over these three nights she foraged in at least 7 distinct locations. The total distance moved per night was 15.5-19.9 km, including return distance to the roost, assuming straight-line movements between hourly fixes. Most foraging was done less than 6 km from the roost. The ratio of total distance moved in a night to the mean distance of forage sites from roosts was similar between nights (3.1-4.3), suggesting that a single roost site to forage site distance recorded during this study can provide an index of total foraging distance. Land tenure status identified for foraging and roosting positions recorded for P. alecto emphasises the lack of protection for habitats used by this species. Only 3% of foraging or roosting positions were recorded in any type of conservation reserve.