X‐ray reflectivity has been utilized in a study of the SiO2/Si interfacial structure for dry oxides grown at room temperature on highly ordered Si(001) surfaces. Scattering near (±110) demonstrates the Si lattice termination of the wafers studied is characterized by a highly ordered array of terraces separated by monoatomic steps. Specular reflectivity data indicate the ‘‘native’’ dry oxide thickness is approximately 5 A˚ with a 1‐A˚ vacuum interface width. Residual laminar order in the oxide electron density along the oxide/Si interfacial normal decays exponentially from the oxide/Si interface with a ∼2.7‐A˚ decay length.