The protocol provided in this document is to replace the previous Provincial Sediment Bioassessment Protocol (Lomas and Krantzberg, 1988). The procedures can be used in the evaluation of contaminated sediments by providing information on lethal and sublethal biological effects. Test applications include the assessment of sediments at remedial action plan sites, general surveillance and monitoring and spills action. In addition, it is intended to be used for the assessment of acute toxicity as prescribed in the "Guidelines for the Protection and Management of Aquatic Sediment Quality in Ontario" (Persaud et al., 1992). This document provides a background and rationale for sediment bioassessment and provides detailed methodology for conducting sediment bioassays and for the rearing and maintenance of test organisms.