This environmental impact statement (EIS) assesses Lease Sale 170 proposed for August 1998 and comprised of 363 lease blocks in the Beaufort Sea planning area. The analysis addresses the significant environmental and socioeconomic concerns identified in the scoping process. Scoping consisted of input from State and Federal agencies, the petroleum industry, Native groups, environmental and public interest groups, and concerned individuals. The potential effects expected from the interaction between environmental resources and OCS-related activities were determined with respect to available scientific information and traditional knowledge. This EIS incorporates information from the Final EIS for the Beaufort Sea OCS Sale 144 (USD01, MMS, 1996a).