The concept of critical values in the medical laboratory found its roots in clinical pathology nearly 40 years ago. The goal of this review was to trace the evolution of the critical value concept from clinical into anatomic pathology with specific emphasis on cytopathology. Difficulties in the meaningful application of the critical value concept in the practice of cytopathology are reviewed along with ambiguities that have yet to be fully resolved. Suggestions that may enhance the operational success of critical value policies in cytopathology and a central role for the cytotechnologist are presented. Cooperation between key pathology and clinical organizations is essential for improvement in the critical value process. Copyright © 2011 American Cancer Society.