This document describes a proposed approach and methodology, which is under development, for comparing the ecological risk of pesticides and their uses in the Environmental Protection Agency's (EPA or the Agency) Office of Pesticide Programs (OPP). Risk assessors are often asked to compare the ecological risks posed by different pesticides registered (or being considered for registration) for use on a specific crop. Comparative analyses can help to ensure consistency in risk management decisions and to focus more significant ecologically-based risk management decisions on those pesticides that pose the greatest risk to fish and wildlife. Therefore, OPP seeks to define standard methods for comparative ecological risk assessment that are scientifically sound and capable of being implemented using currently available data and resources. We would expect to update or replace these methods as additional data and probabilistic assessment tools become available.