Background South Korea has experienced rapid economic development and a substantial increase in life expectancy in an extremely short period. Whether this rapid development has been able to adequately address inequalities in health in South Korea may have important policy implications. This paper explores long-term trends in inequalities in mortality related to education in South Korea between 1970 and 2010. Methods We used secondary data on population size and deaths in 1970 and 1980 from a previously published study, and census and death certificate data from Statistics Korea from 1990, 1995, 2000, 2005 and 2010. Trends in age-standardised mortality rates for men and women aged 25-64 according to education, as well as the rate ratio (RR), rate difference (RD), relative index of inequality (RII) and slope index of inequality (SII), were examined over the period 1970-2010. Results Despite overall mortality declines of 70-80% in the past 4 decades, educational inequalities have increased or been stagnant. There was minimal decline in mortality since 1970 in South Koreans with only a primary or lower level of education. The RR and RD between tertiary education and primary or lower education increased over the study period, while the RII and the SII in both genders remained stable. Conclusions The South Korean experience over the past 40 years suggests that plummeting mortality rates and huge advances in education at the population level do not translate into reduced educational inequalities in mortality.