Abstract GUPCO (Gulf of Suez Petroleum Company) is the largest operator in Egypt. The last 2-1/2 years activity level has been high, with an average of 10-12 rigs operating, and annual footage drilled in excess of 600,000' [183,000 m]. Straight hole turbodrills and polycrystalline diamond compact (PDC) bits have improved drilling efficiency in the Gulf of Suez (G.O.S.) since their initial use in April 1983. Applications in mature fields and areas where conventional drilling techniques had been optimized have benefited from the infusion of this new technology. Although PDC turbine applications in both the 12-1/4" [311.15 mm] and 8-1/2" [215.9 mm] hole sizes have been successfully undertaken, the majority of our turbodrilling experience is in the 12-1/4" [311.15 mm] section. Accordingly the primary focus of this paper will be 12-1/4" [311.15 mm] bit runs. We have identified successful applications in various lithologies using both water and oil base drilling fluids. This paper documents some of GUPCO'S turbine-PDC successes and failures and outlines the analytical process which we are using to optimize our application selection.