We followed up all the infants born to the married women under 50 years of age residing in Gunwee county, Kyungpook Province, between 1 April 1985 and 31 March 1987, and those born to the married women under 50 years residing in Hapchun County, Kyungnam Province, between 1 March 1987 and 28 February 1988, to their first birthday. Likewise, we followed up the infants born to the women who visited the MCH Center of South District Health Center in Taegu City for delivery between 1 April 1985 and 31 March 1987 to the 27th day after birth and obtained the infant mortality rate and the neonatal mortality rate, respectively. There were 17 infant deaths among 1,359 live births in Gunwee and Hapchun Counties and the infant mortality rate was 12.5 per 1,000 live births. Out of 17 infant deaths, 82.4 percent were neontal death and 17.6 percent were postnonatal deaths. Out of the 6,001 live births born to the women visited the MCH Center, 4,834 infants (80.6%) were followed up to the 27th day after birth. Of these 4,834 infants, 36 infants died before the 28th day after birth and thus the neonatal mortality rate was 7.4 per 1,000 live births. Comparison of the maternal characteristics and the birth weight between infants who were followed up and those who were lost to follow-up showed no significant differences. Assuming that the neonatal and postneounatal mortality ratio had been 6:4, the infant mortality rate for the infants born at the MCH Center would have been 12.3 per 1,000 live births. Taking such findings into consideration as the infant mortality rate observed in Gunwee and Hapchun Counties, the neonatal mortality rate at the MCH Center, the causes of infant deaths, and the low birth weight incidence rate, a conservative estimate of infant mortality rate of Korea would be between 12 and 15 per 1,000 live births in $1985{sim}1988$.