Masticatory forces associated with porcelain and acrylic resin occlusal surfaces on osseointegrated implant-supported prostheses opposing natural teeth were studied in five healthy subjects. A three-channel electronic force transducer carrying a fixed prosthesis with either acrylic resin or porcelain occlusal surfaces and balanced articulation was used to record masticatory forces while the subjects chewed various foods. It was found that mean peak masticatory forces varied considerably from subject to subject but were consistent within each subject. No differences related to tooth material could be detected in the load rates. Forces directed away from the implants were noted in all subjects. Keywords: acrylic resin, dental implants, force, occlusion, porcelain