In this article, Gillian Booth, Director at Westgate Laboratories, describes the problem of blanket worming of horses and how this can lead to worm resistance to important drugs. Booth covers in detail the history of anthelmic use, illustrating how the move to over-the-counter worming products is causing issues with resistance in the present day. Further to this, the author explains how resistance may develop and covers a variety of practical steps to slow it down. She concludes that there should be more of a focus on routine testing, rather than worming, to reduce the problem of resistance going forward.