For this 3rd edition of Hairdressing Science the text has been completely reviewed and updated to follow the scheme set out by the Hairdressing Training Board for the National Vocational Qualifications Level 2 in Hairdressing. A change of emphasis reflects the growing concern for the safe use of chemicals and the assessment of health hazards. Throughout the book students are alerted to the effects of the misapplication of chemical products and the misuse of appliances. Features of this edition include a new section on Afro hairdressing, considerable expansion of chapters on hair condition and the use of conditioning treatments, a glossary for quick reference and the addition of groups of questions for student self-testing. In one important respect the book has not changed. Science is still integrated closely with hairdressing and in this way the relevance of science to hairdressing is maintained. Once again I wish to express my thanks to my former colleague John Eaton of Nelson and Colne College for valuable technical discussions, information and advice.