Although attacks on humans by Australian magpies (Gymnorhina tibicen) are a source of significant wildlife-human conflict in urban areas of Australia, little is known about the patterns of attack by these birds. Such information is essential for the development of sound management plans for this species. We examined the attack behaviour of 48 aggressive magpies from Brisbane during September-October 1999, paying particular attention to the types of intruders targeted. All attacking birds were male. A clear majority (71%) of birds attacked only one intruder type, with about half attacking pedestrians only; similar proportions targeted cyclists (8%) only and mail deliverers (10%) only. While all intruding cyclists and mail deliverers were attacked, magpies did not attack all pedestrian intruders, suggesting possible discrimination within this category. Management implications for these intruder types are discussed.