本研究試圖瞭解立委在兩種代表行為──立法問政與選區服務──上的表現，以及影響立委不同表現的原因。過去對立法問政與選區服務的研究傾向認為二者是為兩難或互補，前者的論點在於國會議員的資源是有限的，當他花許多的資源在其中之一種活動時，必然無法兼顧另一種活動；而後者的主要論點在於當國會議員努力於一種活動時，必然緩和了來自於另一種活動的壓力。但本研究以第三屆立委為研究焦點，採用問卷訪問與內容分析方法，研究結果發現：跨不同的立委作比較，立法問政與選區服務行為並不是負方向的關係，而是沒有必然的關係，也就是說，在立法問政較用心的立委並不見得一定較疏於選區服務；同樣的，對選區服務較用心的立委也不見得一定較疏於立法問政。 其次，就立委個人而言，立委必然對於他身為一個代表的角色有所期許，此一期許反映了立委的選區、政黨、以及立委本身的政治目的、資源與經歷，而進一步會影響他在代表方式上作選擇，或者是偏重選區服務，或者是偏重立法問政。根據 Logit 模型的檢証結果顯示，選區因素是影響立委代表行為的最重要因素，那些票源愈集中的立委，愈傾向作選區服務，反之，票源愈分散的立委愈傾向作立法問政。除此之外，政黨的歸屬、黨內競爭程度、立委的政治目的、資深度、是否擔任黨職、以及委員會活動等

This paper examines representative behavior of Taiwan's legis-lators and the reasons for their representative behavior. The rep-resentative behavior is divided into two categories: activities in the Legislative Yuan and activities in constituencies. Some researchers argue that these two categories of representative behavior are a trade-off, because legislators' resources are limited. Others argue that making efforts on one of these two categories of activities may reduce pressure from the other one. However, this paper indicates that these two arguments are not true for Taiwan's legislators. Based on a survey on legislators' assistants and a content analysis up-on Legislative gazettes, this paper shows that the relationship of these two categories of behavior is not necessarily negative. That is to say, the legislators who make efforts in the Legislative Yuan may not necessarily ignore the constituencies. On the contrary, the legislators who make efforts in the constituencies may not neces-sarily ignore the activities in the Legislative Yuan. Secondly, the research findings indicate that individual legisla-tors must have some expectations on their representative roles, and hence these expectations affect their choices on legislative career, either pays more attention to law-making or to constituency ser-vices. Meanwhile, these expectations are affected by the factors related to legislators' party, constituency, and their own political purposes and resources. Furthermore, comparing these influential factors, I find that the factors related to the constituency are the most important. The legislators whose votes are concentrated on a certain part of the electoral district tend to make more efforts in constituencies. On the other hand, the legislators whose votes are scattered across the electoral district tend to make more efforts in the Legislative Yuan. Meanwhile, the research findings show that the following factors affect legislators' representative behavior: party affiliation, the degree of intra-party competition, political purposes, seniority, whether holding a party position, and the ac-tivities in committees.