The local application of lysophosphatidyl choline (LPC) by microinjection into the region of the corpus callosum of the rabbit produced demyelinating lesions. The lesions were assessed histologically using the Luxol fast blue myelin stain and the Holmes silver nitrate stain for the axis cylinders. Survival times for the animals ranged from 7 to 14 days. The center of the lesion was marked by infiltration of macrophages and necrosis, but the major area of the lesion was characterized by demyelination. By consideration of anatomical factors influencing LPC diffusion and of the appropriate placement of the injection, the entire vertical extent (about 0.5 mm) of the corpus callosum could be demyelinated with minimal amounts of necrosis. Since focal demyelination was possible in the fine caliber axons of the corpus callosum which are anatomically representative of many forebrain fiber systems, and since this fiber system is amenable to chronic physiological investigation, the corpus callosum may serve as an experimental model for morpho-physiological studies of mammalian central demyelinating pathways.