目的：本研究旨在了解一大型醫院的投入對當地民眾就醫流向的影響，同時觀察對當地診所造成的競爭壓力，是否會導致基層醫師在診療行為上的改變，包含誘發病人需求。方法：針對臺北市一新設醫院所在地區的居民，利用自然實驗的設計，在醫院成立前後，以問卷訪視的方式對一群成人民眾進行訪談，了解其就醫選擇之變化，並探討西醫診所醫師的某些診療行為是否有改變。結果：本研究發現受訪民眾習慣於區外就診的比例，由原先的42.2%降為30.9%。而習慣在醫院看門診的比例，則由47.7%升高為58.0%。另外，研究也發現，民眾最近一次看門診時，醫師要求複診或自 費買藥或做檢驗的比例有些微下降的情形，而到診所看病的自付費用則沒有明顯的改變。結論：新醫院的成立，明顯地改變了當地居民的就醫流向，但並未造成該區西醫門診市場的激烈競爭，也沒有發現醫師誘發需求的現象。

　　　　　Objectives: This study is to evaluate the impact of a newly opened hospital on local patient flow and to examine the possibility of physician-induced demand due to increased market competition.Methods: A natural experimental study design was employed. Local residents were selected and interviewed before and after an opening of a nearly hospital. A questionnaire was designed to detect the changes of interviewees' selection of health care providers and local physicians' behavior.Results: The proportion of cr oss-area outpatient visits decreased from 42.2% to 30.9%. The rate of hospital-based outpatient visits increased from 47.7% to 58.0%. The rates of physician-initiated re-visit and required laboratory examination both decreased. Patients?out-of-pocket price for a visit was not changed in the research area. Conclusion: The opening of the new hospital changed the interviewees' selection of health care providers, but did not make the local market more competitive. Therefore, this study found no evidence conce rning physician-induced demand.