The purpose of this multicenter, prospective clinical study was to assess the treatment results following endodontic therapy using a glass ionomer cement sealer (Ketac-Endo) and to relate the results to various clinical factors. A total of 486 teeth were treated by three operators, using the "standardized technique" for canal preparation and either single cone or laterally condensed gutta-percha, in one or multiple treatment sessions. Six to 18 months postoperatively, the treatment results were assessed clinically and radiographically, and related to preoperative, intraoperative, and postoperative factors using a chi 2 analysis with 5% level of significance. Of 378 followed-up teeth, there was a 78.3% success, 15.6% incomplete healing, and 6.1% failure. Statistically, differences in the results were related to the number of canals (p < 0.04), primary treatment and retreatment (p < 0.02), pulp vitality (p < 0.001), periapical lesion (p < 0.001), preoperative symptoms (p < 0.003), operative complications (p < 0.001), and absence of restoration (p < 0.03). It was concluded that these treatment results were compatible with those reported in previous studies, and supported the clinical use of Ketac-Endo as an acceptable endodontic sealer.