Contamination of environmental samples and measurement systems can be monitored through the systematic use of appropriate quality control (QC) blanks. During the last decade, a proliferation of terms for these QC samples has taken place, making the specification of appropriate blanks and the interpretation of their data a matter of some confusion. Incomplete understanding of the various types of QC blanks, their points of introduction into a sampling and analysis program, and the kinds of information their results provide can: (1) lead to incorrect preparation and use of QC blanks; (2) limit data comparability; and (3) hinder the technical quality review process for scientific reports. An examination of the frequently used terms for, and functions performed by, different QC blanks is presented to provide the environmental community with a means of combatting the inconsistent use and interpretation of QC blanks. (Copyright (c) 1993 Air & Waste Management Association.)