A comparative study of the appropriateness of hospitalization was conducted in the medical departments of two university hospitals in Israel. A cross-section of 297 patients on one hospitalization day was analyzed using the Appropriateness Evaluation Protocol (AEP). Data were independently collected by two reviewers (R1 and R2). The study revealed a significant difference in the percent of inappropriate hospitalization between the two hospitals, i.e. 13.3% (R1) or 19.3% (R2) for hospital B, and 24.5% (R1) or 32% (R2) for hospital A. The reviewers were in agreement regarding evaluation (92.6%, Kappa 0.78) of 275 index days. A multivariate analysis of the index days with agreed appropriateness correlated with occupancy and length of stay. Routine monitoring of appropriateness of hospital stay should, therefore, be targeted to medical departments with relatively low occupancy rates and/or prolonged average stay.