 The Vienna Circle was a group of scientifically trained philosophers and philosophically interested scientists who met under the (nominal) leadership of Moritz Schlick for often weekly discussions of problems in the philosophy of science during academic terms in the years from 1924 to 1936. As is not uncommon with such groups, its identity is blurred along several edges. Not all of those who ever attended the discussions can be called members, and not all who attended did so over the entire period. Typically, attention is focused on long-term regulars who gained prominence through their philosophical publications, but even these do not in all cases fall into the period of the Vienna Circle proper. It is natural, nevertheless, to consider under the heading “Vienna Circle” also the later work of leading members who were still active in the 1940s, 50s and 60s. Finally, there is the so-called periphery of international contacts and visitors that prefigured the post-World War II network of analytical philosophers of science. In the present article the emphasis will be placed on the long-term regulars whose contributions will be followed, selectively, into the post-Schlick era.