This is a revised edition of the 1988 guide, now including over 300 plants and 100 fungi, and adopting the common name usage of wild plants from the book New Flora of the British Isles (1991). The purpose of this publication is to provide information on plants found in Britain that are known to have adverse effects on people or animals, either here or abroad. It is intended as a layman's guide, but is also a reference tool for doctors, veterinarians and farmers.