This document supplements existing nutrient criteria guidance (USEPA 2000a, 2000b, 2001, and 2008) by providing detailed approaches for estimating and interpreting stressor-response relationships for developing numeric criteria to address nitrogen/phosphorus pollution. The intended audiences include state, tribal, local, and regional scientists who collect and analyze field data in support of criteria derivation. Other stakeholders may find this document useful as well. The guidance assumes readers have graduate-level training or experience in both aquatic sciences and statistics.