Langmuir-Schaefer (LS) monolayer films of fullerene-bis-[4-diphenylamino-4"-(N-ethyl-N-2"'-ethyl)amino-1,4-dipheny l-1,3-butadiene] malonate, 1, sandwiched between two Au electrodes, exhibit pronounced current asymmetries (rectification) between positive and negative bias at room temperature, with no decay of the rectification after several cycles. The device shows symmetrical through-space tunneling for a bias up to +/-3 V, and asymmetrical, unimolecular, "U" type rectifier behavior in the voltage range from +/-3.0 to +/-5.4 V. with rectification ratios up to 16.5. The rectification is ascribed to the asymmetric placement of the relevant molecular orbitals, with respect to the metallic electrodes.