The biology of solid tumor metastasis has been the subject of significant scientific and clinical interest for years and while experimental evidence reveals that metastasis is not solely a random event, very little is known about the biology of metastasis originating from prostate cancer. This is in spite of the fact that the majority of prostate cancer patients die with metastatic lesions to the bone. Progress in understanding this most important aspect of prostate cancer has been hampered by the lack of suitable animal models and an inability to accurately quantify bone metastases and their responses to therapy. Over the past decade, scientists in Japan and the United States have steadily advanced our understanding of the cellular, molecular and immunologic biology of primary and disseminated prostate cancer. It is this body of new information, combined with advances in imaging techniques and prostate cancer tumor markers, that prompted the need for an in-depth assessment of bone metastasis of prostate cancer. Accordingly, on December 12, 1990, a group of basic and clinical investigators from Japan and the United States convened in Gotenba, Japan, to hold the first conference devoted solely to the basic biology and clinical aspects of bone metastases originating from prostate cancer. The cross-fertilization of ideas that was fostered through in-depth discussion of technological advances among various basic and clinical disciplines not only further advanced our understanding of prostate metastases to the bone, but suggested approaches for precise quantitative assessment of these lesions and their treatment.