Drug Information Centers are responsible for providing updated, relevant drug information on the efficacy, safety and quality of drugs as well as disease status to health-care practitioners and finally to patients. This study was designed to revise the drug information service based on the evaluation to meet the social requirement that is created by the recent "Drug Prescription and Dispensing Law" A retrospective analysis was conducted from April 1997 untill September 2000. To evaluate the trend of service, the evaluated period was divided in 7 6-months intervals. The feedback system was used to measure the satisfaction score as an outcome. Out of 618 total enquiries, 192 (31.0%) was received in the last 6-month period. The method of receiving and providing drug information by Drug Information Research Institute (DIRI) gradually changed from telephone calls to e-mailing system (2.2% vs. 67.2% in question, 2.2% vs. 70.3% in answer). Drug information questions concerning the pharmacology (18.8%), adverse drug reaction (10.5%), availability (10.3%) and drug interaction (5.2%) were asked most frequently. The median time to respond the inquired questions was 24 hours (range: 1 hr-8 days). The reference used most frequently to answer was the tertiary literature (42.0%) followed by the second literature (27%) and primary literature (7%). The evaluable 29 feedbacks showed that DI services provided by DIRI were satisfactory in accuracy and time. On the basis of the analysis and evaluation of this project, DIRI have developed the more specified Q and A Sheet Form, systemic database and on-line Q and A corner accessible through the homepage.