Invasive pests cause huge losses both to agricultural production systems and to the natural environment through displacing native species and decreasing biodiversity. It is now estimated that many thousand exotic insect, weed and pathogen species have been established in the USA and that these invasive species are responsible for a large portion of the $130 billion losses estimated to be caused by pests each year. The Agricultural Research Service (ARS) has responded with extensive research and action programs aimed at understanding these problems and developing new management approaches for their control. This paper provides an overview of some of the ARS research that has been conducted on invasive species over the past few years and addresses both different categories of research and some specific pest systems of high interest to the US Department of Agriculture. Published in 2003 for SCI by John Wiley & Sons, Ltd.