This study analyses how the economic interests of a company's largest shareholders affect the choice of secondary equity offering (“SEO”) floatation methods, forms of underwriting agreements with investment banks, and ultimately, the new share issuance price in a SEO where the information asymmetry is high amongst the largest shareholders, investment banks and investors. Unlike price discovery through bookbuilding process, issuing companies and investment banks determine issuance price prior to the offering in Korea. The SEO floatation methods and forms of underwriting agreement are publicly disclosed. This study differs itself from previous studies in that it evaluates how the economic interests of the largest shareholders as well as potential conflicts of interests amongst SEO participants may impact the selection of SEO floatation methods and forms of underwriting agreement. Furthermore, this study, by presenting the drivers behind a SEO and by analysing its effects, is anticipated to contribute to future research related to securities issuance, which is one of the most important financial decisions for corporations. The largest shareholders are seeking not only economic profits from SEO but also noneconomic objectives such as strengthened management control of the corporation. Investment banks tend to prioritize the relationship with the largest shareholders of the issuing company over the interests of retail investors. The forms of SEO can be classified into rights offering, rights offering with under subscribed shares to be offered to the public(“ROUP”), public offering, and 3rd party allotment. There are two types of underwriting agreements which include underwriting agreements on a firm commitment basis and best efforts basis. This study excludes cases where SEO is based on 3rd party allotment as well as those cases where underwriting agreements are non-existing. This study examines which floatation method of SEO is preferred according to the stakes of the largest shareholders and also identifies the financial variables which may have impact on the floatation method of SEO and forms of underwriting agreement chosen. Firstly, based on the analysis of precedent SEOs, we found that the higher the stake of the largest shareholders or the healthier the profitability and financial structure of a company, rights offerings is most preferred and public offering is least preferred. ROUP comes in between the rights offerings and public offerings. The main reason behind such outcome comes from the economic incentives of the largest shareholders. The largest shareholders take advantage of the situation where they possess superior information on the company relative to the retail investors. When the largest shareholders have higher stakes and therefore more economic interests, they tend to get more involved in the SEO process which could affect the economic benefit of minority investors and try to maintain or increase their existing stakes or trade preemptive rights to pursue economic interests. When the largest shareholders have lower stakes and therefore less economic rights, as long as the management control is secured, they tend not to commit more capital to maintaining their stakes not to share potential economic gains with outside investors because they've already disposed of significant stakes. Instead they'd rather seek another investment opportunity. In addition, outside investors would consider the largest shareholders' trading of preemptive rights negative so that public offering is likely a choice of SEO floatation method in this case. Secondly, under ROUP, issuers prefer underwriting agreements on a firm commitment basis to minimize largest shareholders' potential economic losses associated with under subscribed shares. The largest shareholders influence issuers to negotiate with investment banks to reflect their interests in the underwriting agreement. The less reputable investment banks aggressively take the risk of entering into an underwriting agreement on a firm commitment basis to get mandated for the SEO. The largest shareholders prefer underwriting agreement which guarantees that new shares be fully subscribed not to suffer from losses associated with under subscription which in turn has a negative effect on stock prices. On the other hand, in the case of public offerings where retail investors participate, the economic interests of the largest shareholders are less of importance and thus, issuers are indifferent to either form of underwriting agreement. Thirdly, under ROUP and underwriting agreements on a firm commitment basis, the level of discount and underpricing of issuance price is higher than that of the other SEO methods. This is the outcome of compromise of the conflicts of interests between the largest shareholders who want guarantee of the success of SEO and investment banks which want to minimize their underwriting risks. On the other hand, under underwriting agreements on a best efforts basis, because investment banks do not bear underwriting risks and only focus on the sale of new shares, they are not sensitive to the issuance price so there is no incentive for them to reduce the level of discount and the issuance price.