本文建立一個類似Eaton and Grossman (1986) 之三國模型，除將廠商競爭策略之選擇內生化外，亦允許競爭的產品屬替代或互補，並以此一模型檢討出口國政府之最適貿易政策。本文發現：當兩國出口商面對的是「價格與數量」的集合，並且同時自此一集合中選擇其最適值時，廠商之Nash均衡有四重解（即同時存在四個Nash均衡）。一國政府最適政策之方向（課稅或補貼），端視此四個Nash均衡所在的位置與出現的可能性而定，與產品之替代或互補無關。此外，若兩國出口廠商在決策時，先選擇競爭策略（價格或數量），再選擇其最適值時，則當兩國出口品互爲替代品（互補品）時，數量（價格）競爭為兩國出口商之優勢策略，產品市場的Nash均衡爲唯一。此時本國政府的最適政策必然為對其出口品補貼（課稅）。 這些結果均與Eaton and Grossman (1986) 乙文之結論有很大之不同。

This paper sets up a three-country and two-firm model similar to Eaton and Grossman (1986), but allowing the competition mode of its firms to be determined endogenously, and use it to examine the export policy of the exporting countries. It is found that if each firm determines its mode and value at the same time, there are multiple Nash equilibria and the optimal export policy can be either a tax or a subsidy, depending on which equilibrium comes out. On the other hand, if the firms deter­mine the modes before the values, quantity (price) appears to be the dom­inant strategy in the mode selection and an export subsidy (tax) is called for if the goods produced by the two firms are substitutes (complements). These results differ from the findings of Eaton and Grossman (1986).