A polychrome stain for differentiating precollagenous and collagenous fibers, and tetracycline for labeling bone changes were used in young rats to trace adjustments involved in movements of teeth within bone. Distinct differences were seen in fibrous attachments on depository and resorptive bone surfaces. These are associated with shifts of the periodontal membrane as the root and surrounding bone undergo drift. Some resorptive areas receive total destruction of fibrous attachment. Other areas involve a process of fibrous conversion as ordinary fibers of the bone matrix become uncovered during bone removal and function as periodontal fibers anchored into the receding bone surface. An intermediate zone of the periodontal membrane functions to progressively shorten distal ends of these same fibers and to relink them with newly formed precollagenous fibrils. These become continuous with mature fibers attached to the cementum. On depository surfaces, outer fibers of the membrane become embedded into new alveolar bone, and former precollagenous fibrils of the inward-shifting intermediate zone translocate to become the new outer zone. Continuous relinkage is simultaneously maintained between the inner and outer zones. Haversian remodeling occurs beneath resorptive surfaces and re-anchorage is thereby established in specific areas where total destruction of fibrous connection had previously occurred.