The objectives of this study are to analyze, based upon agency theory, empirically the relevance between ownership structure and corporate performance. In this study, samples are 285 firms listed in Korea stock exchage from 1990 to 1994. The results of this empirical test are summarized as follows : Insider-equity ratio of firm in Korea has been positively correlated with performance of corporate. This study intended to present the desirable implecations for seperation of ownership and management.