Two papers recently published in Environmental Toxicology and Chemistry have made important advancements toward understanding the effects of perfluorooctane sulfonate (PFOS) on aquatic life, especially fish. Zebrafish had been identified in a previous study of limited scope as being among one of the most sensitive aquatic species to PFOS, and the results of that limited-scope study have influenced PFOS water quality criteria derived by some regulatory agencies, including the Australian Environmental Protection Agency (EPA).