The good result of this congress (the fifth of the series), in terms of quality of papers and number of participants, proves we were on the right track when in 1974 we founded the International Society for Twin Studies, and even more proves that the interest in gemellology is increasing.

I wish to thank our many colleagues who contributed to the promotion, construction and success of this field of biomedical research, and particularly Gordon Allen, Ian MacGillivray, Walter Nance, Paolo Parisi, and of course Aldur Eriksson.

For my part, I would like to emphasize that going from the title “Study of Twins” given to my book in 1951 to the word gemellology placed in the title of our quarterly Acta Geneticae Medicae et Gemellologiae in 1952, I wanted to affirm: first, that the study of twins is a branch of modern genetics; second, that the study of twins represents a “logos,” that is, a subject composed of acquired concepts, of constant phenomena and specific methods of research on twins in normality, in pathology and in population. With this word, now also adopted by Professor Nance in his Presidential Address, “Introduction to Gemellology,” twin research has become an identified field of science.

In order that the Amsterdam Congress may be as fruitful as the previous ones, I believe it useful to look out of the window of the future with you to see some roads which could be new frontiers of gemellology.