When setting national drinking-water quality regulations and standards, many countries consider the WHO <I>Guidelines for drinking-water quality</I> (GDWQ). To better understand the extent to which the GDWQ are used and reflected in these standards, this global review summarizes information from 104 countries and territories on values specified in national drinking-water quality standards for aesthetic, chemical, microbiological and radiological parameters.<br> The information provided will support regulatory agencies and other key stakeholders to access and compare data when setting or revising national drinking-water quality regulations and standards.