The safety and effectiveness of the disinfectant Triocide for use in water treatment systems is examined. Interviews and a literature review were used to draw the following major conclusions: (1) Triocide seems to be safe, simple, and effective in the short term, with distinct operational advantages over other currently available technologies. (2) Triocide does, however, leave a significant iodine residual in the treated water, raising questions of possible iodine toxicity. Reducing this residual increases the risk of pathogen survival in treated water from subsequent recontamination. (3) Expert opinion differs regarding medium- and long-term iodine toxicity. Continuous use of water with iodine residual for periods of up to 3 weeks poses no significant hazard (according to the Environmental Protection Agency), but continuous use for years appears unwise. No exact dividing line currently exists between "short-" and "long-term" periods, and decisions about "medium-term" use should reflect local conditions and the feasibility of alternative technologies.