The relatively new practice of bringing together for more or less informal conferences a small number of men who are acknowledged leaders in their respective fields for the purpose of discussion of problems in which they have a common interest is gaining increasing currency in many areas. The report of the transactions of the Second Conference on Blood Clotting and Allied Problems, held in New York on Jan. 24 and 25, 1949, indicates clearly how effective such conferences can be in catalyzing the exchange of information among persons with closely related problems to their mutual benefit, and how effective in clarifying issues and aims, resolving semantic difficulties, and bringing moot points into active debate.