內部人知悉內線消息後，在消息未公開之前買賣股票，是否足以構成內線交易？或必須證明內部人有實際利用內線消息的事實，才能構成？這個問題學說見解不一，法院判決亦未盡一致。本文依序討論美國法院有關獲悉說與利用說的爭辯，2014年歐盟相關規定與司法判決，及我國證交法的規定與法院重要判決。本文結論認為，依證交法現行規定，應採獲悉說。最高法院主流見解認為，內部人獲悉內線消息後，在消息未公開前買賣股票，即已構成內線交易。此項觀點，符合證交法的文本及禁止內線交易的目的，應予支持。

Is an insider’s knowing possession of material, nonpublic information at the time of the trade sufficient for insider trading liabilities? Or is a showing of trader’s actual use of the information in making his trading decision required? Legal commentators and court decisions are divided on this issue, with some advocating knowing possession standard, and others supporting use criterion. This article offers a comparative study of the issue, and discusses the “possession” versus “use” debate in the United States, the relevant provisions of the EU Market Abuse Regulation of 2014, the scienter element under Taiwan’s Securities Exchange Act (the “Act’) and the judicial decisions. The author concludes that knowing possession is an appropriate standard to determine insider trading liabilities under the Act. This standard best conforms to the text, the legislative history, and the purposes of the Act prohibiting insider trading.