The goal of this volume is to comprehensively cover a highly readable overview on our present knowledge of positive and negative effects of UV-exposure, with a focus on vitamin D and skin cancer. Topics that are discussed in-depth by leading researchers and clinicians range from the newest findings in endocrinology, epidemiology, histology, photobiology, immunology, cytogenetics and molecular pathology to new concepts for prophylaxis and treatment. Experts in the field as well as health care professionals not intimately involved in these specialized areas are provided with the most significant and timely information related to these topics. It is the aim of this book to summarize essential up-to-date information for every clinician or scientist interested in how to balance between positive and negative effects of UV-exposure to minimize the risks of developing vitamin D deficiency and skin cancer.