The thought of keeping sheep or cattle without being able to rely on any anthelmintic to control worms or external parasites is frightening. With effective treatments currently available, it is easy to forget that parasites can have a massive influence on animal performance. But reports of anthelmintic resistant worms and scab resistance to synthetic pyrethroids are becoming increasingly common in UK sheep flocks. The sheep industry has already banded together to come up with a strategy to slow resistant worms developing in the form of the Sustainable Control of Parasites in Sheep guidelines and is now working on guidelines for ectoparasites. However, this will only be effective in tackling resistance problems if all flocks start following the guidelines. Otherwise the problem will quickly spread as sheep are traded. While fewer cases of resistance in cattle have been reported, there is a great risk that this will become a problem too. This supplement aims to assist producers in making the right product choice for stock, as it lists them according to their anthelmintic group. It also includes a brief overview of the main SCOPS recommendations, to allow producers to make a quick check that their flock or herd policy is going in the right direction. The full document can be accessed free for a more detailed check on www.nationalsheep.org.uk or ask a vet or consultant to assist with individual plans.