Control of viruses in drinking water is critical for public health, and disinfection is the primary barrier against disease-causing microorganisms. UV disinfection is now the method of choice for wastewater and is becoming a very important tool for disinfection of large and small drinking water systems due to the concerns over chlorination byproducts and the need to inactivate Cryptosporidium. Cell culture infectivity data generated over the past 10 years on UV treatment of adenoviruses using 254 nm low-pressure (LP) UV disinfection was used to set 2006 US EPA standards for disinfection requirements of all viruses at a level almost 5 times the typical UV dose of 40 mJ/cm2 used in practice. However, recent research by the PI and various co-investigators has found that use of newer polychromatic UV sources (medium pressure [MP] and pulsed UV) significantly improves the UV disinfection of adenoviruses. These differences between UV sources indicate that a fundamental understanding of how UV irradiation affects adenoviruses is lacking. Numerous authors have called for an increased understanding of the fundamental molecular mechanisms involved in viral response to UV as well as molecular methods for accurate pathogen detection. This research will enhance the understanding of the mechanisms behind UV disinfection of viruses and methods used will provide powerful tools for further disinfection investigations with important positive results for protection of public health.