A new electrochemical probe of Langmuir monolayer films, a continuous interfacial bilayer electrode (CIBE), is described which consists of a hydrophobically modified cylindrical electrode oriented perpendicular to the air/subphase interface. The edge of the electrode is lowered until it just makes contact with the subphase. By rotation of this electrode, fluid Langmuir monolayers are continuously transferred at the instroke of the cylinder and released at the outstroke. The admittance of this rotating cylinder electrode is monitored as a function of molecular area yielding admittance area isotherms which probe the packing and permeability of the transferred monolayers. Measurements of fatty acids of differing chain lengths, lipids, and other surface active molecules are used to show the generality of this new technique.