Invasive animal pests have a wide variety of impacts on the economy, the environment and society. There is considerable information on these impacts for individual cases and regions, and McLeod (2004) attempted to value them nationwide for a whole range of pest animals. However, there appear to be no Australia-wide estimates of agricultural losses measured with the economist's concept of welfare and no national or statewide estimates of environmental loss based on the same concept. In the present report, the direct economic impacts of invasive animals on agriculture in Australia, and the nationwide expenditures by governments and landholders on pest management, administration and research, are estimated. The values of agricultural losses are measured through the concept of economic welfare. The overall impact of pests is calculated here as the sum of the effects on agriculture plus the expenditures on management. The estimates cover the impact on agriculture of four introduced invasive pest animals, namely: foxes, rabbits, wild dogs and feral pigs. The analysis also includes estimates, taken from literature, of the impact of birds on horticulture and mice on grains.