Objective: To improve patient safety and possibly prevent mortality from adverse events (AEs) in hospitals, it is important to gain insight in their underlying causes.We aimed to examine root causes and potential prevention strategies of AEs in deceased hospital patients. Methods: Data on 571 AEs were used from two retrospective patient record review studies of patients who died during hospitalization in the Netherlands. Trained reviewers assessed contributing factors and potential prevention strategies. The results were analyzed together with data on preventability of the AE and the relationship of the AE with the death of the patient. Results: In 47% of the AEs, patient-related causes were identified, in 35% human causes, in 9% organizational causes, and in 3% technical causes. Preventable AEs were caused by technical, organizational, and human causes (78%, 74%, and 74%, respectively) more often than by patientrelated causes (33%). In addition, technical factors caused AEs leading to preventable death (78%) relatively often. Recommended strategies to prevent AEswere quality assurance/peer review, evaluation of safety behavior, improving procedures, and improving information and communication structures. Conclusions: Human failures played an important role in the causation of AEs in Dutch hospitals, because they occurred frequently and they were frequently the cause of preventable AEs. To a lesser extent, latent organizational and technical factors were identified. Patient-related factors were often identified, but the preventability of the AEs with these causes was low. For future research into causes of AEs, we recommend combining record review with interviewing.