ABSTRACT The use of a newly-designed bottomhole assembly in the Kuparuk River Field on Alaska's North Slope has proven to be a cost-effective improvement over traditional rotary drilling methods. The bottomhole assembly consists of a polycrystalline diamond compact bit, a positive-displacement downhole motor with specially-designed tilted drive sub (called a navigation sub), and a measurement while drilling system. The use of these tools in combination allows the driller to constantly monitor the well path and either drill straight ahead or make necessary course corrections, while drilling continues uninterrupted. The savings from such a system have proven to be substantial, with significant reductions in drilling time, increases in rate of penetration, and average savings to the operating company of over $50,000 per well.