Anyone who has more than a slight acquaintance with recent developments in the United States will be aware that there are powerful economic and social forces at work which over the years are likely to modify considerably the related institutional framework. The rapid growth of population and of incomes, and the marked shifts in their distribution within the economy, have already exerted a significant impact on the structure of the banking system, as well as on the pattern of bank assets. Inevitably, these changes have been reflected in money market arrangements, though the major new influence in that sphere has probably been the shift in the climate of opinion about the use and functions of monetary policy. It would be misleading to suggest that there will be any immediate transformation of the American banking scene. The developments that are now attracting attention have been discernible for some time past, but in recent years there has been a noticeable quickening in the rate of change. As a result, the ‘unit banking’ system that has for so long been taken for granted in America is likely in the coming decades to be considerably modified.