This guidance document, developed under SERDP to aid the DoD, presents a current state-of-the-practice overview of available methods, best practices, and key data gaps in assessing the potential for risks from exposure to PFAS for threatened and endangered species at AFFF-impacted sites. It is intended to provide clear guidance to quantitatively evaluate ecological risks to PFAS, and enable site managers to make defensible, risk-based management decisions using the best available information and approaches. The guidance presents clear and specific quantitative recommendations for ecological risk assessments.