Acid-suppressive therapy (AST) is largely prescribed in both hospital and general practice setting but few data are available on appropriateness of AST use in hospitalized patients and its fallout on prescribing in general practice. We assessed AST in patients consecutively admitted to an internal medicine department to determine the type and timing of prescription and indication for use according to widely accepted guidelines. Prescriptions were rated as indicated, acceptable, or not indicated. Overall, 58.7%of 834 admitted patients received AST, mainly proton pump inhibitors. The prescriptions were indicated in 50.1%of patients, not indicated in 41.5%, and acceptable in 6.5%. The main reason for inappropriate use was prophylaxis in low-risk patients (64.8%). On admission, 35.7%of 112 patients already on AST were judged to receive inappropriate prescription; of 348 patients discharged on AST, overuse was identified in 38.5%. No significant difference was observed for inappropriate use at admission, during hospitalization, and at discharge. In 64 inpatients (7.7%) AST, although indicated, mainly for ulcer prophylaxis in high-risk patients, was not prescribed. In conclusion, AST is substantially overused in both hospital and general practice settings, mainly for ulcer prophylaxis in low-risk patients. On the other hand, AST is underused in a small, but not negligible proportion of high-risk patients. Acid-suppressive therapy (AST) is largely prescribed in both hospital and general practice setting but few data are available on appropriateness of AST use in hospitalized patients and its fallout on prescribing in general practice. We assessed AST in patients sequentially admitted to an internal medicine Prescriptions were rated as indicated, acceptable, or not indicated. Overall, 58.7% of 834 admitted patients received AST, mainly proton pump inhibitors. The prescriptions were On admission, 35.7% of 112 patients already on AST were judged to be not in 41.5%, and acceptable in 6.5%. The main reason for inappropriate use was prophylaxis in low-risk patients (64.8%). of 348 patients discharged on AST, overuse was identified in 38.5%. No significant difference was observed for inappropriate use at admission, during hospitalization, and at discharge. In 64 inpatients (7.7%) AST, although indicated, mainly for ulcer prophylaxis in high-risk patients, was not prescribed. In conclusion, AST is substantially overused in both hospital and general practice settings , mainly for ulcer prophylaxis in low-risk patients. On the other hand, AST is underused in a small, but not negligible proportion of high-risk patients.