Abstract The birth rate in Hong Kong fell rapidly from 1961 to 1966: from 35·5 in 1961 to 25·8 in 1966 1 These rates are based on corrected estimates of population and of births made after the 1966 census. They differ somewhat from rates published before that, because the earlier rates had not been adjusted for some underregistration of births and had been calculated on larger population bases than proved to be justified by the census. - a decline of27%. Such a decline deserves special attention, because there are only a few examples of such trends in poor, high-fertility populations since World War II. We have just begun to find evidence of such declines in a few of the other rapidly developing countries of Asia: Taiwan, Korea, Singapore, and Malaysia.