This study analyzed the effect of population control in Yicheng County, Shanxi Province, China. Data were obtained from the 1982 and 1990 censuses, surveys conducted in 1992 in Yicheng County, and Shanxi Annual Reports on Family Planning. The "deferred marriage and reproduction plus interval" policy was instituted in 1985. It established 24 years as the appropriate age for first birth. Women were encouraged to bear a second child at 30 years of age and to stop at 2 children. The government designated Yicheng as a county to be evaluated by the UN. The county's total population was 282,715 in 1994. During 1982-90, the population growth rate was 8.4%, which was lower than the national average of 12.4%, the provincial average of 13.7%, and the Linfen Prefecture average of 14.5%. In 1989-90, the county's birthrate was 0.9% lower than the national average, 3.2% lower than the province, and 4.2% lower than the prefecture. The total fertility rate (TFR), in 1989, was 2.28 children/woman, which was lower than national, provincial, and prefecture TFR. A comparison of the age-specific fertility curves shows the county with later starting ages and a high narrow peak, which suggests lower childbearing after the age of 30 years. 52.5% of births, in 1989, were single parity. The sex ratio at birth during 1985-90 has been within the normal range, with 1 exception. Unauthorized double parity declined from 48% to 6.7% during 1984-86. The abortion rate declined from 0.90 to 0.20 during 1984-92. The program impact was much greater during 1985-97.