Dr Henry Lim, renown for expertise and research in photodermatology leads this issue of Dermatologic Clinics. Photodermatology in this issue addresses dermatoses brought on or accelerated by light as well as light forms for dermatology therapies. Photodermatology is used to diagnosis and treat many common conditions that bring patients to the dermatologist. Topics include: Introduction to photobiology; Evaluation of patients with photodermatologic conditions; Photoimmunology; Photoaging; Photocarcinogenesis; Polymorphous Light Eruption (PMLE); Actinic Prurigo; Hydroa vacciniforme and solar urticaria; Chronic actinic dermatitis; drug-induced photosensitivity; Cutaneous porphyrias; Photoaggravated dermatoses; Ultraviolet (UV) based therapy; Photodynamic therapy; Photoprotection. Dr Lim works with one his residents, So Yeon Paek, as his co-Editor on this issue.