Background In recent years,the incidence of unexplained sudden death has risen significantly across the world.However,it occurred suddenly,often in young apparently healthy individuals and almost 50％ of the patients did not have any wing signals or symptoms.Therefore,the prodromal symptoms before the incident are extremely important for early prediction of sudden death.In this article,we aimed to explore the value of prodromal symptoms for unexplained sudden death and whether the prodromal symptoms have a predictive function to unexplained sudden death (USD)without underlying diseases.Methods A total of 208 sudden death cases were selected for the survey in the Emergency Department of Peking University Third Hospital from January 2006 to December 2009 and their medical records were reviewed.The patients were divided into two groups,65 patients had underlying diseases while 143 had not underlying diseases.In the meantime,their prodromal symptoms were collected and compared,prodromal symptoms including chest distress,dyspnea,syncope,fever,headache,vomiting,etc.Results Patients with underlying diseases were compared to those without underlying diseases associated with sudden death; there was no significant difference in gender and age distribution.Among the 208 cases,39 cases (18.75％) had prodromal symptoms,patients with underlying diseases had prodromal symptoms in 12 cases (18.46％),while patients without underlying diseases had prodromal symptoms in 27 cases (18.88％).The difference between the two groups with prodromal symptoms was not statistically significant(P＞0.05).Conclusions Prodromal symptoms are extremely important wing signals in the occurrence of USD.It has equally important predictive value for patients both with and without underlying diseases,especially in predicting sudden death caused by cardiopulmonary and neurological diseases.