Ultraviolet (UV) disinfection is an emerging technology for production of reclaimed water, but development and testing are proving its effectiveness. UV disinfection for reclamation requires design criteria much different from those used for conventional disinfection for stream discharge. The basic theory of UV disinfection, the use of UV for production of reclaimed water, and applicable design criteria are discussed. Design criteria are given for process, hydraulic, and control instrumention systems. Major unresolved issues are discussed including virus inactivation requirements, a proposed new indicator organism for viruses, and the need for different levels of process monitoring. Specific design details for projects being designed in Hawaii, at Lahaina and Kihei, are presented. Future trends in UV disinfection and water reclamation are discussed.