Purpose: This article proposes a classification protocol for reporting the outcome of implant overdentures. Materials and Methods: Review of the literature pertaining to postinsertion prosthodontic procedures for maxillary and mandibular implant overdentures revealed a wide range in the terminology used and methods of reporting outcome, usually as a result of the use of varying designs among different implant systems. A need for comparative evaluation of the prosthodontic success of implant overdentures was identified. Results: An existing classification protocol for implant-fixed prostheses containing six objectively defined fields was modified for implant overdentures. This new protocol, which also uses the descriptive fields of success, survival, unknown, dead, and retreatment (repair or failure), provides a method whereby postinsertion prosthodontic procedures and subsequent time to retreatment can be quantified regardless of design, method of attachment, or implant system. A ratio method for identifying prosthodontic treatment cost effectiveness of implant overdentures is included. Conclusion: This protocol could assist clinicians in their choices of implant overdenture therapy by providing accurate comparisons of varying implant overdenture systems and designs, and by identifying prosthodontic treatment cost effectiveness.