To determine the extent of inappropriate hospital use, to investigate factors related to variations in appropriateness, and to identify reasons for inappropriateness, the Appropriateness Evaluation Protocol (AEP) was applied to 2067 patient days in two hospitals between March 1997 and 1998 in Ankara, Turkey. A substantial amount of inappropriate utilization was found in both hospitals (34.2%, 24.6%). Factors affecting the appropriateness of hospital utilization and reasons for inappropriateness were varied and presented by internal medicine, general surgery, and gynecology services. In general, results of the logistic regression analysis indicated that inappropriateness was significantly associated with admission number (first admission/readmission), admission route (emergent/non-emergent), and day of the week. The most common reason for inappropriateness was diagnostic procedures and/or treatments that could have been carried out on an ambulatory basis. This study demonstrates that the AEP can be used as a tool to improve the efficiency of the Turkish hospitals.