Mica has been made hydrophobic by a novel approach using Langmuir-Blodgett deposition of prepolymerized octadecyltriethoxysilane (OTE). The mica was activated by treatment in a water/argon plasma before deposition of the OTE. On baking the OTE-covered mica sheets at 100-degrees-C in a vacuum oven for 2 h, hydrophobic surfaces with an advancing water contact angle = 112-degrees are obtained. Contact angle studies, contact thickness measurements, and evaluation of the quality of contact between two OTE-covered mica surfaces when examined using the surface force apparatus indicate that the OTE deposit is a robust monolayer which is resistant to chemical displacement by potassium ions. Surface energies of these hydrophobic surfaces are in good agreement with published data for hydrocarbon surfaces.