Readmissions after an acute care hospitalization are frequent and associated with significant burden for patients and healthcare systems. Overall, 14-22% of the patients are readmitted within 30 days after discharge of an acute care hospitalization. A recent systematic review showed that interventions could reduce rates of readmission, but also that the most successful interventions are the most complex ones. Therefore, to be efficient, we need to target these intensive discharge interventions to the patients with a high risk of readmission. The HOSPITAL score has been shown to accurately identify medical patients at high risk for 30-day readmission and is currently one of the best validated readmission prediction models, with good performance showed in 5 countries and nearly 150,000 patients. In this seminar, I will present the development and validation of the HOSPITAL score, and discuss some of the challenges faced during the international validation study.