We report experimental electrical characterization of Al/AlOx/molecule/Ti/Al planar crossbar devices incorporating Langmuir–Blodgett organic monolayers of eicosanoic acid, ‘fast blue’, or chlorophyll-B. Current–voltage and capacitance–voltage measurements on all three molecular device structures exhibited controllable switching hysteresis. Control devices containing no molecules showed no evidence of switching. A model of interface trapped charge mediating electronic transport appears consistent with all of the data. This data illustrates the importance of considering the complete device system (consisting of the molecules, the electrodes, and the interfaces) when analyzing its electrical behavior.