How the United States and Canada approach the process and implementation of drinking water standards is critically examined. Despite many similarities in their approaches to regulating drinking water contaminants, there are a number of important differences, including approaches to dealing with genotoxic versus presumed epigenetic carcinogens and selection of biostatistical quantitative risk assessment models. Such international comparisons provide a valuable means to discern how others have attempted to solve similar problems and thereby provide an excellent opportunity to test the validity of one's own methodologies.