Canada goose droppings, collected in parks to which the public had access, were screened for a range of bacteria that could be pathogenic in man. Droppings of Canada geese, and other waterfowl, did contain such bacteria, including some that are well-known causes of illness in man. These bacteria, plus a species of Salmonella that was experimentally inoculated into droppings, were shown to survive and multiply in the droppings for up to one month after their deposition by geese. Canada geese ranged further from water than other waterfowl species and thus distributed their droppings over a larger area of park grassland. This more widespread distribution of their droppings leads Canada geese to pose a greater potential health risk than other waterfowl studied here, but variations in human responses to challenge with bacteria, and variations in human and waterfowl behaviour in public parks, renders quantification of this risk impossible.