Autotransplantation of 33 maxillary canines was followed up in 29 patients with an average age of 27.5 years. The mean follow-up period was 6.0 years. Endodontic treatment was performed in 23 teeth. Signs of root resorption were found in an increasing number of canines during the follow-up period. At the last examination eight canines showed no signs of resorption. External and internal resorption of inflammatory type were the most frequent forms of resorption and were also found to be the most hazardous factors for the prognosis of the transplanted tooth. Extraction of the transplant was necessary in four cases because of root resorption or poor bone regeneration.