Foxes, wild dogs, feral cats, rabbits, feral pigs, and feral goats are believed to have deleterious impacts on native biodiversity in Australia. However, although considerable resources have been expended controlling these six pest species, there are few reliable estimates of the effects of pest control on native biodiversity. We first show why reliable knowledge of the effects of pest animal control operations can be gained only by adopting proper experimental designs (i.e. treatment and non-treatment areas, replication, and random assignment of treatment and non-treatment areas) and monitoring of both the pest and biodiversity. We then review the design of 1915 pest control actions conducted with the aim of protecting native biodiversity in Australia during 1990–2003. Most (67.5%) pest control actions consisted of a single treatment area without monitoring of either the pest or biodiversity. Only 2.4% of pest control actions had one or more treatment and non-treatment areas, and very few treatment and non-treatment areas (0.3%) were randomly assigned. Replication of treatment and non-treatment areas occurred in only 1.0% of pest control actions. The field of wildlife management has been strongly criticised for its slow adoption of the tenets of experimentation to examine the effects of management actions, and our results show that this criticism applies to mammalian pest control in Australia. Until the principles of experimental design are adopted, knowledge of the effects of mammalian pest control in Australia will remain unreliable.