The International Society for Twin Studies is a unique organization. It is unique in the status of members composing the Society. In addition to specialists of science and medicine we have non-specialist members including twins and their families, all enjoying excellent collaboration in undertaking research and related activities of common interest. This kind of collaboration is very important for academic societies, particularly for those devoting themselves to the studies of man. We aim at a better understanding of man; our purpose is to learn more about ourselves. This activity is not a monopoly of specialists. Our achievements should also be shared by lay people. ISTS can serve as a model for academic societies aiming at the studies of man. Science has the solid ground of logos. At the same time, we realize that the accomplishments of highly specialized science should be reevaluated in the light of human values. I am inclined to believe that our task is to integrate the logos of scientists and ethos of the public into one.

The purpose of twin studies is two-fold; studying multiple birth phenomena per se, and making inquiry into the genetic and environmental sources of human variation. The latter task was initiated by a number of pioneers in the early twentieth century. At that time, however, genetic studies of man including twin studies remained largely descriptive. We could not, and still cannot, perform genetic experiments on human individuals and populations, and the methodology available was limited to observation of a character presented in pedigree members and twins. However, despite the limitation of methodology, classical pedigree analysis has permitted us to accumulate a large amount of data on normal hereditary traits and genetic diseases, or more precisely, simple Mendelian characters.