Grey squirrels (Sciurus carolinensis) have spread rapidly since their introduction into Great Britain in the late 19th century, and Ireland in the early 20th century. They have a significant impact on woodland biodiversity and, in particular, the native red squirrel (Sciurus vulgaris). Grey squirrels have displaced red squirrels throughout most of England and Wales, central and southeast Scotland, and parts of Northern Ireland, through competition and disease. Grey squirrels also pose a threat to the sustainable management of woodlands through the damage they cause to trees by bark stripping. Such damage may lead to a loss of particularly vulnerable tree species (e.g. beech) within the canopy of woodlands and this may be accompanied by a decline in associated fungal and invertebrate fauna. In some areas it can act as a disincentive to the creation of new woodlands for timber because it reduces the value of the trees. In many areas of the UK, grey squirrels are unaffected by predation and therefore targeted control is often necessary to reduce their impact on woodlands and biodiversity. This Technical Note provides updated information on methods of grey squirrel control. It has been produced in response to changes in legislation as well as recent developments in control methods and trap designs.