SummaryTrauma from occlusion was induced by inserting cantilever bridges bilaterally in the mandibles of two monkeys. In one monkey the mandibular nerve was cut on one side; in the other on both sides. By this procedure possible protective action of nerve receptors in the periodontal membrane was reduced. The occlusal trauma resulted in severe damage to the pulp and resorption of the roots, but no appreciable downgrowth of the crevicular epithelium.