Thick marine sedimentary sections and geologic structures favorable for the accumulation of petroleum are indicated in Georges Bank basin, the Baltimore Canyon trough, and the Southeast Georgia embayment. Undiscovered recoverable resources of petroleum on the Atlantic OCS are estimated to be 10 billion to 20 billion barrels of oil and 55 trillion to 110 trillion cubic feet of gas. Such estimates carry a high degree of uncertainty. Preliminary results suggest that the most favorable areas for leasing are under the deeper waters of the shelf.