Current–voltage characteristics are reported as a function of temperature (2–300 K) for 2.8-nm-thick eicosanoic acid (C20) Langmuir–Blodgett organic monolayers sandwiched between planar platinum electrodes of area 5–200 μm2. An exponential temperature dependence observed between 60 and 300 K does not fit standard activated conduction, but can be described by thermionic field emission through a thin ∼0.1-eV barrier. A second model of tunneling through a vibrationally excited harmonic oscillator barrier also fits the data. A broad ∼200 meV dip in conductance at V=0 suggests strong inelastic tunneling, supporting the vibrational model.