Objective: To compare the degree of root resorption in endodontically treated primary molars with that of homologous teeth without root canal treatment. Method and Materials: A retrospective study was carried out comprising 105 records of children who had received root canal treatment in a primary molar. Mean age at the time of treatment was 7.0 ± 1.4 years. Inclusion criteria included one endodontically treated primary molar and a homologous primary molar with no root canal treatment on the other side of the mouth. All teeth were treated by the same operator in the same way using the same iodoformcontaining root canal filling material. The degree of root resorption was compared by radiographic evaluation 12 or more months posttreatment. Results: The degree of root resorption on the final follow-up radiograph in the endodontically treated primary molars was significantly higher (P .05) than the degree of root resorption in the homologous teeth. The degree of root resorption was higher in boys than in girls. No statistical significance was found between the degree of root resorption and the age at the time of treatment in either the root canal-treated teeth or the homologous teeth. Follow-up radiographs demonstrated a higher degree of root resorption in the root canal-treated teeth than in the homologous teeth, regardless of the type of treatment performed on the homologous side. Conclusion: Root canal treatment performed with iodoform-containing root canal filling material accelerates root resorption in root canal-treated primary molars compared with homologous teeth without endodontic treatment. Clinicians should be aware that endodontically treated teeth will probably shed before homologous ones that are not root canal treated. Keywords: Endoflas, primary molars, pulpectomy, root canal treatment