This chapter describes the uncertainty associated with specific measurement endpoints commonly used in sediment ecological risk assessments (SERAs) and discusses approaches for addressing these sources of uncertainty. These step-wise procedures provide explicit guidance on the four major elements of risk assessments, including: problem formulation, exposure assessment, effect assessment, and risk characterization. In addition, several types of measurement endpoints were identified at the Workshop which have been used to conduct these SERAs, including: (1) toxicity tests (both the fraction tested and the endpints selected); (2) benthic invertebrate assessments; (3) bioaccumulation assessments; (4) sediment chemistry; and (5) sediment quality quidelines.