Since their introduction into New Zealand, the Australian bush tail possum, Trichosurus vulpecula, has become a major animal pest. Possums are believed to number over 70 million, and are known to spread bovine tuberculosis, eat pasture and crops, kill young trees in forest plantations, cause severe damage to indigenous forests in conservation areas, and prey directly on insects and young birds. They have no natural predators (apart from humans) in New Zealand and range from the highlands to the coastal areas. Millions of dollars are spent each year by a number of government agencies in an attempt to curb the possum population. This paper explores a number of spatial data issues involved in possum control in an attempt to show how a GIS can assist with possum management on a conservation block. Examples are given using data obtained from a number of control operations on Mount Karioi and using the GIS packages ArcView and ARC/INFO. From the planning stage, through the operation and monitoring stages, GIS has an important role to play in pest management. The broader issues on spatial analysis explored here include remote sensing and image analysis, GPS, buffering, overlay and 3D analysis.