内容提要平行进口叉称灰色市场行为，目前学术界对此现象众说纷纭。本文就中外学者对平行进口产生和发展的原因、可能带来的问题，其对产商利润及其研发活动的影响、对消费者剩余的影响、对社会福利的影响等所作的理论与实践分析进行了一番梳理与评价。笔者认为，平行进口是否会打击厂商研发活动的积极性取决于研发活动前后的利润之差，而不取决于研发活动之前或之后的单一利润水平。平行进口政策的一致化过程也未必是一个零和博弈过程，应该区别对待不同形式的平行进口。

本文建立了一个由两个国家和两个厂商组成的经济学模型，两个厂商都在同一国家梢售一种同质产品，其中一个介司还通过一个零售商在另一个国家销售其产品，我们发现，在两个国家进行销售的那个公司有时会倾向于引入平行进口来与另外一个公司竞争。这与原生产厂商反对平行进口的理论形成了鲜明的对比。

本文建立了一个平行进口模型，其中一个生产厂商已经拥有一种产品，并考虑开发另一种新产品，通过比较新旧产品的平行进口对厂商产品开发的不同影响，我们发现，对创新产品的平行进口预期或者为遏制创新产品的平行进口所作的可能的努力，更加打击生产厂商从事产品开发的积极性。

In this paper, we develop a differentiated duopoly model with endogenous cost-reducing R&D and review the argument on welfare effect of price and quantity competition in the presence of technology licensing. We show that the standard conclusion on duopoly (Singh and Vives, 1984) can be completely reversed. Cournot competition induces lower R&D investment than Bertrand competition does. Moreover, Cournot competition leads to lower prices, lower industry profit, higher consumer surplus and higher social welfare than Bertrand competition.

In this paper, we develop a vertically differentiated duopoly model where a high-quality producer competes against a low-quality producer, a la Cournot competition. The high-quality firm has both a new technology and an obsolescent technology. After first deciding whether to license, the firm then chooses which of the two technologies to license. We show that, irrespective of the licensing contract, licensing the new technology is always superior to licensing the obsolescent technology. This finding poses a sharp contrast to the conventional wisdom.