To comply with the maximum contaminant level (MCL) for total trihalomethanes (TTHM), many utilities have modified their pre-oxidation and disinfection practices by switching to alternative oxidants and disinfectants in place of free chlorine. To evaluate the impact of these changes, a research project was initiated to study several water treatment plants that had recently adopted the use of chlorine dioxide, ozone, potassium permanganate, or chloramines to partially or fully offset the use of free chlorine. The results of the study showed that total organic halide (TOX) formation paralleled THM formation at all eight of the utilities investigated. The alternative pre-treatment oxidants and disinfectants were depleted rapidly as a consequence of the high TOC concentrations in the waters examined. This implies that residual oxidants and disinfectants and oxidation effectiveness to be reduced.