Dermatologists are presented with a diversity of therapeutic modalities for the treatment of inflammatory, sclerosing, and neoplastic conditions, but with the development of various new irradiation devices that utilize specific parts of the electromagnetic spectrum, phototherapy has become a more viable, accessible, and efficacious option in the treatment of these conditions. The ultraviolet (UV) range (10-400 nm) is further subdivided into UVA and UVB, each of which has been particularly useful in a number of skin conditions. The most commonly used forms of UV irradiation are UVA1, psoralen plus UVA (PUVA), and narrowband (NB) UVB. Each of these modalities differ in their mechanism of action, indications, and side effect profiles, and it is important that clinicians be familiar with these differences. Today, phototherapy is a valuable option in the treatment of many nonpsoriatic conditions including atopic dermatitis, sclerosing skin conditions such as morphea, vitiligo, and mycosis fungoides. Due to its relative safety, phototherapy may be used in most populations, including children and pregnant women. However, contraindications and side effects are known and should be considered before patients begin a phototherapeutic regimen.