Summary Korea is one of a number of East and South-east Asian countries for which there is evidence of declines in period fertility rates. Between 1960 and 1970, the total fertility rate in Korea decreased by roughly one-third. There has also been a reduction in the interval between marriage and first birth and an increase in age-specific fertility among younger women. Information on the mean number of children ever born to ever-married women after specified durations of marriage is analysed to document the changing tempo of Korean fertility. Results indicate that there has been a steady increase in the number of children born during the early years of marriage among women first married between 1936 and the late 1960s. Reasons for the observed changes in the timing of fertility are specified, and the implications of such changes for population growth in Korea are examined.