The Fifth Annual Meeting of the Japan Endocrine Pathology Society was held in September 2001. A highlight of the meeting was the participation of Japanese and American endocrine pathologists in a conference to consider the topic "The Determination of Clinical Outcomes for Parathyroid Carcinomas by Histological Evaluation of Invasive Growth." The discussion was centered around three cases of parathyroid carcinomas selected by the coordinator, Dr. Kameyama, and discussed by Drs. Ronald DeLellis, Ricardo Lloyd, and Kennichi Kakudo. In this article, we summarize their diagnoses and comments.