PIP: Demographic changes have occurred continuously in Korea as a result of contraception and these have in turn resulted in general social changes. The family planning program, in place for 25 years, has greatly contributed to fertility decline as well as socioeconomic development. As a result, the total fertility rate has declined to 2.1, or population replacement level, in 1985. It is crucial to analyze the fertility trend which has had the most significant influence on demographic change and thus on population policy decisions and the formulation of population policy measures. The authors analyzed the changes in fertility between 1972-85 using statistical data published by the Economic Planning Board. Annual births occur mostly to women in their 20s. In 1972, 60.2% of annual births were to women in their 20s while 36.3% were to those women age 30 and up. However, by 1985, 86.7% were to women in their 20s while only 10.5% occurred to women 30 and older. The proportion of lower birth order has been increased and the proportion of higher birth order has been decreased. The proportion of 1st birth order increased from 26.7% in 1972 to 51.4% in 1985, and that of 2nd birth order increased from 23.7% to 38.3% during the same period. As a result, the proportion of both 1st and 2nd birth order increased from 50.4% to 89.7% during the same period. Increase in the proportion of the lower birth order and decrease in the proportion of higher birth order are common to all age groups of mothers. These results mean that the fertility level dropped in general and this is a remarkable in the 1980s. The fact that the proportion of a lower birth order is higher in Korea than in China or Japan provides an index to future fertility trends. These phenomena are due to the successful family planning programs, to social support policy measures for family planning enacted at the end of 1981 in line with the 5th 5-year Economic and Social Development Plan, and to the 1-child family campaign begun in 1983. The impact of population policies on demographic change is so great that the necessity of continued research on demographic changes and related fertility changes must be emphasized. In addition, a comparative study with other countries which have already experienced demographic transition could provide guidance to policy formulation and flexible policy direction. (author's modified)