Sudden cardiac death (SCD) has not been investigated separately in Greece. The aim of this study is to describe the epidemiological characteristics of people dying suddenly out of hospital in an area of Greece. In 1990, a population based study was started to detect the cases of people dying suddenly out of hospital (< 1 h after onset of acute symptoms or < 6 h after being seen alive) in a closed population in Northwest Greece (Ioannina area: 160,000 inhabitants). During a 3.5 year period, 283 potential cases aged 30-70 years were identified by monitoring the mortality in the emergency rooms of the two hospitals of the area, the coroner's office and the death certificates from the Government Department of Statistics. The diagnosis of SCD was established in 223 (183 men, 40 women; mean ages 59 and 61 years respectively) after visiting and interviewing the relatives and/or the family doctors within 12 days (range 1-28) after the death. SCD in the study accounts for 50% of all cardiovascular deaths and is the most common cause of death after neoplasia. The most common place of death was home (151 cases, 68%), and in 174 cases (78%) deaths occurred while the patients were relaxing or during routine activities. Prodromal symptoms were reported in 57 cases (26%). The time of day of death showed a circadian variation, with a peak in the late morning from 9:00 to 12:00. Ninety four (42%) had a prior history of heart disease. One hundred and ninety one cases (86%) occurred in the subgroup of age 50-70 years.(ABSTRACT TRUNCATED AT 250 WORDS)