The Interior Dept. proposes 20 lease sales in 8 of the Outer Continental Shelf planning areas in the Gulf of Mexico and offshore Alaska during the period 2002-2007. Activities that could occur on leases issued may extend over a period of 25-40 years. These activities were analyzed for environmental impacts: (1) drilling oil and natural gas exploration and production wells; (2) installing and operating offshore platforms and pipelines, and onshore support facilities; and (3) transporting oil using ships or pipelines. The specific amounts and locations of activity that might occur are unknown. This analysis is based on reasoned assumptions about future activities. Vol. I: text; Vol. II: charts and tables.