AbstractWater quality‐based limits are receiving greater emphasis in National Pollutant Discharge Elimination System permits. These permits often contain requirements for conducting acute or chronic toxicity tests of wastewater and/or ambient receiving waters. In this paper, we analyze the effort (in person‐hours per test‐ph/t) required to conduct the 7‐d fathead minnow (Pimephales pro‐melas) larval survival and growth test, the 7‐dCeriodaphnia dubiasurvival and reproduction test, and various tasks that are associated with these two static‐renewal tests (e.g., maintaining cultures of the test animals, water chemistry analyses, quality assurance/quality control needs, sampling, and reporting). This analysis shows that all of these tasks require 53.6 ph/t. For six samples (e.g., five ambient samples plus a control, or five concentrations of an effluent plus a control), the fathead minnow test requires 6.9 ph/t and theCeriodaphniatest requires 5.8 ph/t. The effort needed to maintain fathead minnow cultures is approximately equal to that needed to maintainC. dubiacultures (5.6 vs. 5.8 ph/t). Effort expended on other components of the testing includes 7.0 ph/t for water chemistry analyses (six samples), 5.5 ph/t for test preparation and takedown, 4.0 ph/t for QA/QC, 6.0 ph/t for report writing, and 7.0 ph/t for sampling. In addition, the analysis explores the economies of scale in conducting the two toxicity tests. Finally, the study provides guidance for those who plan to conduct these tests and for those sponsors who may need a better understanding of the basis for the c