The relative hydrophobicity of surfaces containing highly regular, nanoscale (< 100 nm) topological features (50 nm diameter, 5 nm height, 100 nm spacing) was measured and compared with their flat counterparts. The results are described in the context of both the Wenzel and Cassie models for wetting rough surfaces. Wenzel-type wetting is observed for these high areal density nanostructures (similar to 10(10)/cm(2)) whose aspect ratios range from 0.2 to 0.7.