This paper reports the empirical evidence on the relationship between the ownership structure and firm value. Specifically, the effects of institutional ownership, foreign ownership, individual ownership and large shareholder ownership on the value of the firm are examined over the period of 1993-2004. In particular, the paper focuses on the change of these relationship after the IMF bailout since it had such an enormous impact on Korean economy. In the analysis we control for the cross-sectional and time series effects by incorporating industry dummies and year dummies. Since the value of institutional ownership is directly affected by the changes of firm value, institutional investors have a strong incentive to monitor the managers. Institutional investors induce managers to make more voluntary announcements and reduce the discretionary decision making that may have a negative effect on firm value. On the other hand, the institutional ownership can have a negative impact on firm value if the interests of managers and institutional investors are so aligned that the monitoring disappears. The empirical evidence indicates that the institutional ownership has a positive relationship with the firm value. After the IMF bailout, the influence of institutional ownership became stronger. There has been much discussion on the role of institutional investors for the improvement of corporate governance especially after the IMF bailout and the result is consistent with this. Foreign investors could be very effective in monitoring managers since they are independent of the managers. Under the situation in Korea wherein the owner managers are so powerful that the effective monitoring is difficult, the foreign investors can have a very positive impact on firm value. On the other hand, the firm value may decrease if the foreign investors hold the ownership only for the very short period of time and push the firm to pay too much dividends. The results show that there was no influence of foreign ownership on the firm value. After the IMF bailout, however, the influence of foreign investors got stronger to have a significant positive impact on firm value. This reflects the fact that the more liberalized capital market due to IMF bailout made the influence of foreign investors become stronger in the Korean market. If the ownership is diversified to many individuals, the free rider problem makes it difficult to monitor the managers. Since many new measures have been introduced to protect the minority shareholders after the IMF bailout, the negative effect of diversified individual ownership would become weaker after the IMF bailout. Consistent with the argument, the results show a (-) sign for the individual ownership variable. But the statistical significance is so weak. And there was no perceptible change in the relationship between individual ownership and the firm value after the IMF bailout. This reflects the fact that the new measures introduced to protect minority shareholders are not yet effective in Korea. The existing literature reports that there is a non-linear relationship between the large shareholder ownership and the firm value. As the large shareholder ownership increases the firm value also increases since the conflict of interests between shareholders and managers are getting smaller. After a certain level of ownership, however, the firm value begins to decrease as the management entrenchment gets stronger. The results show that there is a monotonic negative relationship between the two variables. As for the chaebol firms the firm value increases as the large shareholder ownership increases up to 15%, but decreases thereafter. On the other hand, the value of independent firms monotonically decreases as the large shareholder ownership increases. Differently from the US the major agency conflict in Korea is the one between major shareholder and minor shareholders rather than the one between managers and shareholders. Therefore, the ownership increase of the large shareholders reinforces the entrenchment of them exerting a negative impact on firm value.