This paper presents existence and sources of long-term reversal in the Korean stock market. During the past 15 years, return reversals from the past performances of individual stocks, which are listed in the Korean Stock Exchange, existed significantly, in terms of buy-and-hold abnormal returns. We found that cross-sectional contrarian premiums over 1- to 36-month holding periods were significantly positive during the period of Aril, 1987 to April, 2002. The sources of these premiums, however, were differently analyzed according to the past portfolio formation periods. In the 12 months formation period, the contrarian premiums were found to result mainly from the systematic risk factors of Fama-French 3 factor model, but the premiums in the 24 and 36 months formation periods were not due to the systematic risk factors, but to the hypothesis of behavioral finance that the overreaction increases with the length of formation period. Additionally, we analyzed the sources of contrarian premiums in the two sub-sample periods, up- and down-market periods. In the down market period, co-skewness factor premiums were found to play an important role for explaining the contrarian premiums, but in the up market period, contrarian premiums were found to be an evidence of weak-form market inefficiency which could not be explained from any asset pricing model.