Water-poor coastal regions of the world are turning increasingly to desalination of seawater for supply. Tampa, Florida has a plant under construction and San Diego, CA is considering one. In addition, the State of Texas is evaluating a large-scale desalination demonstration project for several sites along its Gulf Coast. While much of this desalination relies on membrane process sites where electrical power is generated using steam are uniquely suited to distillation processes. The Water and Power Authority of the USVI (WAPA) has operated hypobaric distillation desalination plants on the three major islands for over 10 years. The two major plants each provide potable water for populations of about 50,000 persons. In the last two years one of the islands experienced a sudden increase in TTHMs at the long-residence-time site (LRT). This increase was roughly concomitant with changes in passivation for corrosion control in the distribution system and a number of other changes, including several in disinfection practices. Unlike most THMs in most systems, those in the WAPA system were between 50% and 70% bromoform, with up to 90% brominated species. Efforts of the Authority to address the problem are reviewed in this paper and the possible contribution of electrolytic generation of mixed-oxidant disinfectants is discussed, along with a review of the possibility of passivation chemical addition contributing to the problem. A factor most likely to affect isolated systems subject to severe interruptions in production, such as can result from hurricane damage, is the large amount of finished water storage required against such interruptions. It was found that several factors contributed to the problem, including automatic disinfectant rate control, operation of storage facilities, instantaneous water supply demand changes and possibly application of mixedoxidants generated on-site. For each contributing factor the corrective actions taken by the Authority and their results are presented. At this point, only a single, under-utilized part of the system does not comply with DBPR Stage 2 requirements and proposed corrective action for this area is also presented. [Pontius(1999)] Includes 13 references, tables, figures.