Book excerpt: Hair is subject to either intrinsic (i.e. physiological) aging or extrinsic (i.e. premature) aging that can be attributed to external factors. The intrinsic factors can be associated with genetic mechanisms and are subject to individual variations, whereas external factors include ultraviolet radiation, air pollution, smoking, and possibly nutrition. Leading experts have contributed to this book which offers a practical approach to the evaluation and management of various forms of alopecia, including their pathogenesis, the diagnostic procedures involved, medical treatments, and nutritional issues. A completely new surgical technique for hair transplantation that leaves behind sufficient follicle unit tissue to regenerate hairs is also described. Being comprehensive and easy-to-read, this book should be very useful for dermatologists who wish to diagnose and treat their patients with hair problems more effectively.