Aims and objectives: To study the prevalence, characteristics and circumstances of unexpected in-ward deaths in a Belgian university hospital, in order to delineate future prevention strategy. Methods: Twelve year review. Unexpected in-ward deaths were listed from a local questionnaire (database) on the characteristics and circumstances of each in-hospital death. Comparison of variables was made with expected deaths. Medical and nursing notes of patients who died unexpectedly were then reviewed, with particular attention to the premonitory signs (abnormal physiological parameters or presumed risk factors) that were possibly documented in the 48 hours preceeding death. Results: Unexpected deaths accounted for 8,3 % (n= 221) of total in-ward deaths. These deaths did not occur preferentially to specific days of the week, but occurred more often during night-time, with a peak in the early morning. In only 9 (4%) cases (p<0,001 vs expected deaths), the family was present at the bedside of the patient at the time of his death. Relative prevalence of unexpected deaths was higher in surgical wards, and most (63%) unexpected death patients had been admitted through Emergency room ; 24.4% had a prior stay in Intensive Care Unit and 35.7% underwent an invasive procedure during their hospitalisation. Identification of a presumed risk factor or detection of abnormal vital signs before death were found in 166 (75,1%) patients; only 49 of these had a written advance care plan found in their file notes. Conclusion: Prevalence of unexpected in-ward deaths is substantial and requires preventive measures. Most patients dying unexpectedly had presented early warning signs within the 48 hours before fatal event. Based on our observations, reinforcing the night staffing of units that admit patients with an acute morbidity profile would be wise. Also, implementing a systematic approach (algorithms) of the acutely deteriorating patients with timely initiation of end-of-life discussions seems essential.