This study is to examine relationships of several socioeconomic position indicators with mortality risk in a nationwide longitudinal study of South Korea. The Korea Labor & Income Panel Study, conducted on a probability sample of urban South Korean households by Korea Labor Institute, contains date of death information for the decedents which were used to estimate relative risks of mortality and their <TEX>$95\%$</TEX> confidence intervals (CI) with Cox regression analysis. A total of 125 men and women among 8,415 subjects died between 1998 and 2002. Socioeconomic differentials in mortality were observed after adjustment for sex and age. Those with less than 12-year education had 1.90 times <TEX>$(95\%\;CI=1.25-2.91)$</TEX> greater mortality risk than those with 12-year education or more. Greater mortality risks were also found among those with low occupational class and manual occupation. The magnitude of differentials in mortality risks between occupational class were similar in two different approaches to measuring women's occupational class: (1) approach 1 where women, married or not, retain their own occupational class, and (2) approach 2 where married women are assigned their husbands' occupational class. Relative risks of dying among those with low household Income were 1.62 <TEX>$(95\%\; CI=1.08-2.42)$</TEX> compared with the counterparts. Those who reported economic hardship at the time of survey in 1998 had greater risk of mortality <TEX>$(RR=1.83,\;95\%\;CI=1.21-2.78)$</TEX> than those who did not. In conclusion, increased social discourse and policy discussions about these health inequalities are needed in Korean society. Future studies should explore the causes and mechanisms of socioeconomic mortality inequalities.