Abstract In analogy to inorganic semiconductor devices tunnel junctions consisting of organic heterostructures incorporated between two gold electrodes are built. Molecular layers are formed by using Langmuir-Blodgett films of two different molecules, a phthalocyanineand a perylene-derivative. Tunnel characteristics at 4.2 K of junctions incorporating two different molecular layers exhibit rectifying behaviour and show equidistant steps in the current, reminiscent of single electron charging phenomena. At higher temperatures the tunneling current is superceded by thermal hopping processes through defect states which over-ride the steplike structure in the curves. The absolute tunneling current through the junction roughly scales with the active junction area.