First stage, nozzle guide vanes and accompanying endwalls are extensively cooled by the use of film cooling through discrete holes and leakage flow from the combustor-turbine interface gap. While there are cooling benefits from the interface gap, it is generally not considered as part of the cooling scheme. This paper reports on the effects of the position and orientation of a two-dimensional slot on the cooling performance of a nozzle guide vane endwall. Inaddition to surface thermal measurements, time-resolved, digital particle image velocimetry (TRDPIV) measurements were performed at the vane stagnation plane. Two slot orientations, 90° and 45°, and three stream wise positions were studied. Effectiveness results indicate a significant increase in area averaged effectiveness for the 45° slot relative to the 90°orientation. Flowfield measurements show dramatic differences in the horseshoe vortex formation.