本文欲探究先進入市場之廠商與後進入市場者在品質與價格競爭上之主動關係，其中後進廠商之成本不僅與先進者之品質決策有關，更與自身品質有正相關。在兩階段非合作賽局下，廠商決策與市場結構將因先進廠商之成本高低而有所不同。當先進廠商之成本較高時，其會利用品質作為市場之進入障礙 (entry deterrence)，使後進廠商無法進入市場。當先進廠商之成本較低時，便無法利用品質策略來阻止後進廠商進入市場，其最適決策為生產最高品質之產品，而後進廠商則為生產最低品質之產品。然而，在此情形下，高品質優勢不必然存在，即生產高品質產品之廠商不一定會獲得較高之利潤。在政府實施嚴格專利權保護下，若先進廠商之成本較大，則專利權保護為較佳之政策；若先進廠商之成本較低，則福利效果不確定：後進廠商之成本愈大、消費者之同質性愈高，及產品品質程度愈低時，專利權保護會導致較高之福利水準。

The paper investigates the interactions between leader and follower firms in a two-stage quality-price game. What differs from the literature is the follower's cost structure, which not only depends on the leader’s quality choice, but also on the follower’s own quality. When the leader firm incurs relatively high costs, it is able to employ quality as a tool to deter entry. If the leader’s costs are low, its optimal choice will be to produce the highest quality, and the follower will subsequently opt to produce at the lowest level of quality. However, the high-quality advantage may not persist under such circumstances. The welfare effect of a strict patent protection is ambiguous, and hinges on the costs of the follower, the heterogeneity of consumers, and the quality of products.