權威控制是一項控制檢索款目的作業，主要在於提高目錄的檢索效能， 進而協助讀者一次找出相關資料;換言之，以改善目錄查詢與書目資料庫品質為 首要任務。當圖書館著手實施或完成書目回溯建檔時，通常將回溯性權威控制作 業一併納入執行。由於圖書館限於人、物力，且基於廠商提供權威控制服務之考 量，因而圖書館常將回溯性權威控制作業委託廠商代為執行。本文試從Blackwell NorthAmerica、Library Technology Inc.及Westerr Lbrary Network三家廠商提供之權威 控制服務作一整體比較，同時針對挑選權威控制服務廠商的評估原則提出說明， 供圖書館參考之用。

　　　　　Authority control is a process of controlling accessing entries. Its main purpose is toenhance the effiency of catalog's retrieval and help the users to find and collocate thedesiring data at one time, in other words to improve the quality of catalog's usage andbibliographic database. When libraries began or finished conversion of bibligraphic records,they always take the authority control into consideration, too. Due to the limited s:aff,budget and vendor's service, vendors do this complicating job for library usually. This ar.icleis to make a comparision among authority control service of the Blackwell North America,Library Technology Inc., and Western Library Network. Finally, the article offers adetailing discussion to select the vendor's service.