RATIONALE AND OBJECTIVES. To investigate the use of ethylcellulose microspheres as long-term and peripheral emboli for percutaneous maxillofacial arterial embolization. METHODS. Eight mongrel dogs were selected randomly for internal maxillary artery embolization with ethylcellulose microspheres. After embolization, angiographic, microangiographic, and histologic examinations were performed. RESULTS. Ethylcellulose microspheres were trapped in the peripheralarterioles from 24 hours to 6 months after embolization. Dcgenerative changes of maxilla, mandible, and dental pulp occurred after the embolization of the internal maxillary artery with the microspheres. No evidence of whole of focal necrosis of the bones and surrounding soft tissues was found between 24 hours and 6 months after embolization. CONCLUSION. Ethylcellulose microspheres can be used as an alternative long-term and peripheral embolic agent, with potential for percutaneous maxillofacial arterial embolization.