政黨與選區是國會議員在國會裡議事所面臨的兩股力量，這兩股力量以不同的程度與方式影響國會議員的代表行為。本文以我國立法委員的代表取向與代表行為為研究焦點，研究發現指出立法委員的代表型態自一九八○年代中期以來，有自政黨取向朝向選區取向轉變的趨勢，對此本文提出一個可能的原因：自有力的反對黨民進黨出現，黨際競爭促使黨內競爭的激烈化，促動了在SNTV選舉制度下的立委去建立個人選票的動機，從而，許多立委在立法院與選區積極表現自己以期獲得選民的注意與支持，有時甚至不惜與政黨的立場相違背。同時，根據對於第三屆立委的研究發現指出：第一，有大約三分之二的立委偏向選區取向，而僅有不到三分之一的立委偏向政黨取向；第二，立委的不同代表取向對其代表行為確實有很大的影響：政黨取向的立委較重視立法表現，而選區取向的立委較重視選區服務；同時，政黨取向的立委較選區取向的立委忠於政黨的立法領導；第三，個別立委的代表取向受到立委的得票方式、政黨歸屬、以及選區型態的影響，如果立委愈需要靠選區的力量才能當選，立委是國民黨籍，或者立委是來自於同質性較高的選區，將愈傾向採行選區取向的代表型態。 Party and constituency are two major forces faced by legislators. They influence legislators' representative behavior in different degrees and in different ways. This paper examines how these two forces influence Taiwanese legislators' representative styles and behavior. Research findings show that the representative styles of Taiwan's legislators have changed radically since the mid-1980s.Many legislators changed from a party-oriented style to a constituency-oriented style. This paper suggests a possible reason for this radical change. Legislators have to build their personal vote because they face intensive party competition resulted from the emergence of an opposition party, the DPP. The legislators under a single non-transferable vote system cannot count only on their party to get re-election. Most of them have to show their distinctive characteristics and hard-working in the legislative Yuan and in their constituency. They may even deviate from the party line to get attention and support from their constituencies sometimes. Based on a case study on the third term of legislators, this research has several findings. First, approximately two-thirds of the legislators are constituency-oriented, and less than one-third of the legislators are party-oriented. Secondly, the representative orientations of legislators affect their representative behavior profoundly. Party-oriented legislators make more efforts in the law-making process, while constituency-oriented legislators make more efforts in their constituencies. Meanwhile, the party-oriented legislators follow the party line more than their constituency-oriented fellows do. Thirdly, the representative orientations of individual legislators are affected by their vote-getting styles, party affiliation, and constituency styles. The legislators who rely more on their constituency than party to get re-election, the legislators of KMT, and the legislators from homogeneous constituencies, are more likely to be constituency-oriented.