A method for measuring the concentrations of the five regulated haloacetic acids (HAA5) in drinking water is reported. This method uses ion chromatography to separate HAA5 species, followed by post-column reaction with nicotinamide and detection of the fluorescent products. The result of method detection limit, accuracy, precision, linearity and interference studies are reported. The on-line monitoring method is compared directly to USEPA 552.3 in Memphis drinking water. Though not meant to replace the USEPA 552.3 for compliance monitoring, the proposed method does offer attractive alternatives considering the ease of automation and application of on-line monitoring directly from drinking water distribution systems.