A number of various federal and state guideline documents that have been issued for use in demonstrations under Section 316(a) of the Federal Water Pollution Control Act contain criteria to be applied in selecting organisms that are representative of the aquatic community at the proposed power plant site. This paper reviews three Section 316(a) case histories in which these selection criteria are applied and evaluates the usefulness and practicality of the methodology. The conclusion is reached that the basic approach of using representative species is practical but that the reliability and accuracy of the selection process is only as good as the available data on the seasonal distribution and life histories of the aquatic community in the receiving waters. A baseline field monitoring program designed to gather adequate data for the Section 316(a) representative species selection and evaluation process is proposed.