This document provides a simple assessment procedure to estimate the responsiveness of a waterbody to changes in the supply (loading) of phosphorus (P) and nitrogen (N). Lakes, rivers, streams, and estuaries may be assessed with this procedure. Few data about the waterbody are required. The procedure consists of a dichotomous key that leads to classifying the waterbody in question according to key characteristics that influence the responsiveness of the waterbody to changes in nutrient loading.