How drinking water standards are set and which contaminants should be regulated are central issues in reauthorization of the Safe Drinking Water Act (SDWA). Suggested amendments to the standard-setting provisions of the SDWA cover a broad spectrum. In general, environmental groups argue that standards are not strict enough and that greater consideration should be given to sensitive sub-populations. Others note that the high cost associated with meeting increasingly strict standards is unjustified in light of the uncertain and sometimes nonexistent incremental benefits. This column takes a look at the issues involved in developing a rational approach for establishing drinking water standards. It reviews the current US Environmental Protection Agency (USEPA) to set standards. The second part of this series will review legislative proposals offered in the 104th Congress to change the standard-setting process. Includes 10 references, table, figure.