The purpose of this study was to examine tooth mobility changes after replantation of avulsed permanent teeth and to correlate these data with radiographic and clinical findings. The material consisted of 35 patients in whom 40 accidentally avulsed permanent incisors were replanted. Mobility testing was performed with a modified macroperiodontometer. Combined clinical, radiographic and mobility findings indicated that healing after replantation could be divided into the following modalities: 1.Normal healingwith slightly increased or normal mobility values and no radiographic sign of progressive root resorption. 2.Permanent replacement resorptionwith lowered mobility values and radiographic sign of replacement resorption. Decreased mobility values indicate that ankylosis was usually evident 5 weeks after replantation. At the same time, it was possible to diagnose the ankylosis by the percussion test. The radio-graphic examination first revealed ankylosis 8 weeks after replantation. 3.Transient replacement resorption(not previously described) with lowered mobility values which later became normal. Radio-graphic signs of a transient replacement resorption were present in some cases. 4.Inflammatory resorptionwith increased mobility values and radiographic sign of inflammatory root resorption. Mobility values tended to become normal when inflammation subsided as a result of root canal treatment.