These proceedings describe a workshop held July 17-19, 1990 in Manitowoc, WI, at which biological remediation of contaminated sediments was discussed. For the purpose of the workshop, contaminated sediments of primary interest were those within six of the Areas of Concern (AOC) identified by the U.S./Canada International Joint Commission's Great Lakes Water Quality Board; five of which are priority concerns of the U.S. Environmental Protection Agency's Assessment and Remediation of Contaminated Sediments (ARCS) program. The workshop was organized around four topic areas: (1) Overview of the Areas of Concern; (2) Biological degradataion of PCBs; (3) Biological degradation of PAHs; and (4) Biological treatment of metal species. For the first topic area, presentations were made describing site characteristic of the Ashtabula River, OH; Buffalo River, NY; Sheboygan River, WI; Grand Calumet River, IN; Saginaw River and Bay, MI; and Hamilton Harbor, Ontario, Canada. For the remaining topic areas, presentations were made by investigators actively involved in either bench, pilot, or full-scale studies concerning these areas. In this document extended abstracts written by the presenters are given, as well as brief summaries of the presentations and discussion sessions.