Objectives To identify the preventability, determinants and causes of unplanned hospital readmissions within 30 days of discharge using a multidisciplinary approach and including patients' perspectives. Design A prospective cross-sectional single-center study. Setting Urban teaching hospital in Amsterdam, the Netherlands. Participants 430 patients were included. Inclusion criteria were: age � 18 years, discharged from one of seven participating clinical departments and an unplanned readmission within 30 days. Methods Residents from the participating departments individually assessed whether the readmission was caused by healthcare, the preventability and possible causes of readmissions using a tool. Thereafter, the preventability of the cases was discussed in a multidisciplinary meeting with residents of all participating departments and clinical pharmacists. The primary outcome was the proportion of readmissions that were potentially preventable. Secondary outcomes were the determinants for a readmission, causes for preventable readmissions,