甲公司王董知悉甲公司的內線消息之後，不是買賣甲公司股票，而是買賣與甲公司的股價具有密切關聯的股票，包括關係企業、競爭廠商、原物料或零組件供應商及工程承包商等。這些公司的股價與甲公司有密切的連動關係，不論是水漲船高，或是此消彼長，都是所謂的關聯股票。買賣關聯股票所引發的內線交易，本文稱之為關聯股票的內線交易。本文依序探討美國及我國規範內線交易的相關法制，最後提出結論。本文認為，如王董所知悉的消息，係因擔任甲公司董事職務所獲悉，且對正當投資人是否投資關聯股票的決定有重要影響，王董在重大消息未公開之前買賣關聯公司股票，對於其交易對手而言，本質上是不公平的交易，應受證券交易法禁止內線交易的規範。

Under the current Securities Exchange Law, Company A’s directors are prohibited from trading Company A’s stocks on inside information. But what if the directors trade instead in stocks of Company A’s rival firms, suppliers, contractors, or affiliates? Are the directors still liable for insider trading? This article first discusses insider trading law in the United States, and then reviews relevant statutory scheme and judicial decisions in Taiwan. This article concludes by suggesting that if the information the directors receive will significantly influence a reasonable investor’s decision for trading in related stocks, the directors are liable for insider trading for two reasons. First, the directors have access to the information as corporate insider. Second, the trade is inherently unfair to those with whom the directors are dealing.