本文嘗試以三階段賽局分析雙占的上游製造商對下游零售商採取不同垂直控制的可行性。在雙占製造商各自面對眾多零售商的市場結構下，製造商必須考慮品牌間的競爭，品牌內的競爭與零售商的牽制力。垂直控制可規避後二者所產生的問題，然而，卻有可能會提昇品牌間的競爭程度。尤其當此二製造商皆以約定轉售價格作為垂直控制的方法時，形同製造商間直接以價格作為競爭手段。在產品完全同質的極端情況下，競爭的結果將使雙方的超額利潤消失殆盡。因此，當上游製造商間的產品同質性夠高時，為避免激烈的品牌競爭，二家上游廠商有可能會採取不同的垂直控制策略。不過，也由於競爭性的降低，消費者反而必須付出更高的價格，而導致社會福利的降低。由此觀之，公平交易法似乎不宜視「約定轉售價格」為當然違法。

We consider the impacts of intrabrand competition, interbrand competition and countervailing power to show that duopoly upstream firms may use asymmetric vertical controls to promote profits. We characterize equilibrium contracts involving a RPM or not when each upstream firm contracts with multiple downstream retailers. When both upstream firms impose a RPM, the two firms seem to compete in a Bertrand final product market. If they produce a homogeneous product, then the profits would drop to none. As the consequence, we may image that if the homogeneity between the two products is high enough, then there is no symmetric RPM contracts. Under this condition, the two upstream firms may provide asymmetric vertical controls to prevent fierce competition.