At temperatures in the vicinity of 100 degrees C, multilayer Langmuir-Blodgett films of cadmium octadecanoate deposited under typical literature conditions undergo a slow phase transition to a columnar phase, in which the molecules are organized into long, laterally dense-packed rods. On the molecular scale, the order in the new phase is identical to that in the stable bulk phase at that temperature, while macroscopically, the substrate is still covered with a uniform film and shows long-range order. The columnar phase is quite stable at room temperature and at temperatures up to at least 140 degrees C.