Among 4371 men aged 35 to 64 in 1973 who were randomly selected, living in Quebec City suburbs, without clinical evidence of ischemic heart disease (IHD) at entry and followed for 16 years, 426 had a first acute IHD event; of these, 296 had a nonfatal myocardial infarction (MI), 50 a fatal MI (death within four weeks of the acute event) and 80 an early death, ie, they died before the diagnosis of MI was made. Among these 80 early deaths attributed to IHD in the absence of any other apparent cause, 55 men died within 1 h from the onset of symptoms or were found dead in their bed (group A) while 25 died more than 1 h after the onset of symptoms (group B). In this population, a first acute IHD event carried a 31% (130 of 426) case fatality within the first four weeks. Groups A and B accounted for 42% (55 of 130) and 19% (25 of 130) of the total acute ischemic mortality, respectively. As expected, fatal events increased with age, but the proportion of early deaths over the total IHD mortality was as frequent in younger men as in older men. Smoking, increased systolic and diastolic blood pressure and serum cholesterol were associated with increased nonfatal events. A similar association, except for serum cholesterol, was observed for all fatal events. No significant risk factor profile differentiated early from late fatal events. In conclusion, in this population, nearly a third of men with a first IHD event died, most of them outside the hospital. None of the main established risk factors differentiated men with a fatal MI from those with an early death.