Abstract: Sudden unexpected natural death (SUND) was uncommon in our environment; with the adoption of western life style and societal pressures this mode of death is becoming more common. Understanding the causes of sudden natural death is important for prevention and improving treatment outcomes. Aim: The aim of this study was to describe the demographic data, the immediate cause of death and associated risk factors in the sudden unexpected natural death (SUND) cases in Imo state. Methodology: The archived case notes, Post-mortem registers and reports in the data bases of Departments of Pathology and Medical records and Biostastics of Federal Medical Centre (FMC) Owerri were used as the sources of data for this study from January 2003 to December 2012. Full post-mortem examinations were performed by consultant pathologists in the department using laid down protocols. Results: The male to female ratio was 3.3:1 with mean age of 45.2 ± 17.0. The age range was 15 to 80 years. The peak age of incidence was in the 41-50 years age group. The leading causes of SUND were the cardiovascular system (CVS) 55.4%, followed by central nervous system (CNS) which made up 23.1%, gastrointestinal system (GIT) constituted 8.5%, the Respiratory system (4.2%), Vascular disorder (4.2%) and undetermined causes (6.4%). The associated risk factors included dietary factors 14 cases (29.8%), alcohol use 9 cases (19.15%), cigarette smoking (17.02%), Diabetes mellitus 6 cases (12.76%), family history 5 cases (10.64%), those without associated factors 3 cases (6.38%) and congenital anomalies 2 cases (4.25%). Conclusion: In Nigeria, with increased western lifestyle, changes in dietary habits and rise in socioeconomic status, cardiovascular diseases especially complications of hypertension has become the most important cause of sudden unexpected natural death in our society. This calls for immediate and effective management of hypertension through effective clinical and public health policy implementation.