We describe subject recruitment and research results from the Osaka University Aged Twin Registry (OUATR). The research focus of OUATR is the genetic and environmental contributions to physical-cognitive-mental aging which we examined in Japanese twins in later adulthood. Within this large-scale registry (12,000 pairs) of oriental twins born between 1900 and 1935, approximately 10% of participants are MZ twins reared apart from early childhood. Two hundred and fifty pairs have had comprehensive medical examinations, including various blood chemical panels, lymphocyte subtests, WAIS (Wechsler Adult Intelligence Scale), and urine analysis. The future foci of this study are primarily on longevity, decline of cognitive functions with aging, bio-physiological functions, lifestyle and behavior genetics, and psycho-spiritual functions.