This paper describes the experiences of a Florida utility before, during and after conversion to chloramines as a secondary disinfectant. Background information for the decision to switch from free chlorine residual to chloramines is discussed. The utility experiences high temperatures, significant total organic carbon (TOC) levels and varying water sources during normal operations. Descriptions of the following are included: development of remedial actions with specific water quality triggers; distribution system flushing operations; and, storage reservoir operation and monitoring. Extensive water quality monitoring programs were conducted to establish baseline water quality prior to the change to chloramines. Organic, inorganic and microbiological parameters were monitored. Changes in distribution system water quality are described including significant increases in total coliform and heterotrophic plate count (HPC) organisms. Change in disinfection byproduct (DBP) concentrations, variations in inorganic parameters, rapid chloramine residual loss, and nitrification are discussed. Customer complaints regarding taste & odor, and rusty water were also experienced. Significant biofilm characterization was done before and after the change in secondary disinfectant using denatured gradient gel electrophoresis, phospholipid fatty acid analysis and other techniques. Samples were collected from pipe coupons removed from distribution system piping and from annular reactors located at various points in the system. In a cooperative study with the Centers for Disease Control, Legionella and Mycobacteria populations in plumbing systems in large buildings and residences were examined to determine the impact of disinfectant change. Apparent increases in algae in the distribution system after chloramination were observed. Includes 6 references, figures.