Phototherapy, or the usage of light to treat diseases, is an important modality in a physician's therapeutic armamentarium. It is effective for a number of common skin conditions like atopic dermatitis, psoriasis and vitiligo. The accurate diagnosis of a photodermatosis or light-related skin disorder relies on a good clinical history and physical examination, supported by diagnostic investigations such as phototesting.Phototherapy and Photodiagnostic Methods for the Practitioner is the first published set of practical guidelines for Asian skin, drawing upon our cumulative clinical experience with phototherapy for various conditions at the National Skin Centre in Singapore, amalgamated with up-to-date evidence from the scientific literature. It is designed to serve as a concise and comprehensive reference manual for dermatologists, as well as clinicians, medical physicists and nurses with an interest in photodiagnostic investigations and phototherapy for the evaluation and treatment of skin disorders.