The disinfection of swimming pools and other recreational water systems with halide disinfectants such as chlorine is a very important and fundamental component of pool operation. One of the negative aspects of chlorine and bromine disinfection is the production of disinfection byproducts (DBP). DBP are compounds formed when chlorine oxidizes the organic contaminants found in swimming pools and pool water. Some of these organic contaminants are present in the source water and many more are introduced through normal pool usage. As organic contaminants are introduced into the pool water by swimmers and other sources, the organic contamination can accumulate in the filter media thereby increasing the overall organic load of the pool. Much of the overall organic load in a swimming pool or spa actually resides in the media of the filtration system. Because of the constant presence of oxidizing levels of chlorine in swimming pool systems, DBP are continually produced while swimming pools are in operation. As chlorine oxidizes the organic contamination in the pool, hundreds of new chlorinated and brominated compounds are formed. Many of these compounds continually build up in the pool water, while others are volatile and move from the water to the air. Numerous studies have determined the identity of many of these compounds and it is now understood that many of them are known to be toxic to humans. Recently there has been increased interest in understanding the effects of exposure to DBP in swimming pools. A number of medical reports have described higher incidences of certain ailents in competitive swimmers and pool workers and have hypothesized a potential role for DBP in the development of these conditions. Since regulations require the use and maintenance of minimum levels of chlorine in commercial pools, the only way to reduce DBP in pools is to reduce the organic load that reacts with chlorine. Sphagnum moss has been in use to treat recreational and industrial water for many years and has many beneficial effects. Sphagnum moss stabilizes water chemistry, reduces overall chemical and water usage, and reduces organic contamination. In this presentation, I will review the relationship between organic contaminants and the production of DBP in recreational water. I will also discuss the ability of Sphagnum moss to reduce the organic contamination in water systems and how this reduction in organic contamination leads to a reduction in DBP levels in swimming pools.