'Trease and Evans' is an encyclopedic reference work on pharmacognosy - the study of those natural substances, principally plants that find a use in medicine. Its popularity and longevity stem from the book's balance between classical (crude and powdered drugs' characterization and examination) and modern (phytochemistry and pharmacology) aspects of this branch of science, as well as the editor's recognition in recent years of the growing importance of complementary medicines, including herbal, homeopathic and aromatherapy. New chapter on 'Neuroceuticals'. Addition of many new compounds recently added to British Pharmacopoeia as a result of European harmonisation. Considers development in legal control and standardisation of plant materials previously regarded as 'herbal medicines'. More on the study of safety and efficacy of Chinese and Asian drugs. Quality control issues updated in line with latest guidelines (BP 2007).