The North Slope is an established producing petroleum province where exploration began in the 1950's. To date, over 35 bnboe has been discovered in the basin, notably in the super-giant Prudhoe Bay and Kuparuk oil fields. The basin is located in a harsh Arctic environment presenting unique challenges for explorers, such as seasonal access, environmental issues, and high costs. Potential for material discoveries exists within the offshore plays, particularly the Chukchi Sea, but in the current environment companies are choosing to relinquish offshore leases, casting doubts over the future of the play. However, recent exceptional onshore exploration success in the emerging Nanushuk play, and also offshore in the Beaufort Sea play, have made Alaska one of the top global exploration targets, particularly onshore. The combined prospective resource, together with relatively favourable access conditions compared with other basins, make it attractive to explorers.