Pulmonary embolism (PE) and deep venous thrombosis (DVT) are clinical manifestations of the same entity, venous thromboembolic disease (VTD). In approximately 25% of patients, the first manifestation of PE is sudden-unexpected death. We carried out a prospective study at the forensic pathology service of the Institute of Legal Medicine in Seville with the aim to know the incidence of PE as well as to describe the epidemiological, pathological and clinical characteristics of these deaths and associated risk factors. In the study period (32 months) 32 cases of PE were registered from a total of 2447 completed autopsies. Three cases were considered accidental deaths and the remaining 29 cases were sudden natural deaths, which represents 1.3% of the total autopsies, 2.6% of natural deaths and 4.3% of sudden deaths. Nineteen cases (59%) were men (mean age 50.3+/-13.8, range 22-74 years) and 13 cases (41%) were women (mean age 50.3+/-13.8, range 18-87 years). In 78% of cases death occurred at home or during transfer to a health care centre, mainly during the fall or winter (69%) and between 8a.m. and 4p.m. (47%). Pulmonary infarction was associated only in two cases (6%). Nine cases (28%) had been immobilized but only three (9%) received anticoagulant therapy. Surgical interventions had occurred in seven cases (22%). A history of psychiatric pathology was found in 31%. Overweight or obesity was found in 75%. The most frequent symptoms prior to death were dyspnea (31%) and chest pain (19%), and 19% of patients were examined in an Emergencies Department for symptoms compatible with deep vein thrombosis and/or PE, but this diagnosis was not suspected in any case. PE frequently makes its first appearance as sudden death. In addition to the classic risk factors, this study highlights that 75% of the cases were overweight/obese as well as 31% having had a history of psychiatric disorders and treatment as to support that this association should be considered as a risk factor. PE continues to be under diagnosed in Emergencies Department patients, which hinders the application of adequate therapeutic measures to prevent these deaths.