本文探討在外國對手廠商對本國廠商的出品成本具有不充分訊息的情形下，本國廠商的出╱直接投資決策。本文的研究結果發現：一、在既定的關稅水準下，廠商決定出口╱直托投資的臨界成本會較充分訊息時的臨界成本為高。二、在既定的國內生產成本下，廠商決定出口╱直接投資的臨界關稅會蠅充分訊息時的臨界關稅為高。當外國的競爭廠商數增加時，本國廠商決定出品或直接投資的臨界成本與臨界關稅都會因而提高。

　　　　　This paper analyzes the export/direct-investment strategies adopted by the multinational firm of the home country under the assumption that a host country's competing firm has incomplete information about the cost of home production of the multinational firm. The main findings are that for a given tariff rate, the critical cost of export/direct-investment is higher under incomplete information and that for a given cost of home production, the critical tariff of export/direct-investment is also higher under incomplete information. As the number of host country's firms increases, the critical cost and/or tariff are also higher.