The number of participants (380) as well as the number of presented papers (182) turned out to be almost the same as the corresponding numbers for the preceding conference of this series in Rome (1970). 23 countries were represented. About 18% of the scientists came from non- European countries. In spite of slightly stricter selection rules for the non-Europeans, this group presented more than 25% of the papers,with the USA contributing by far the highest portion.