The physiopathology of sudden coronary death (SCD) is well known. However, its impact on the population of France has not been studied in depth. The MONICA project recenses all coronary events in subjects of 25 to 64 years of age in a given geographic area. The definition of SCD is coronary death occurring less than one hour after the onset of symptoms. Out of 4,004 coronary deaths recorded from 1985 to 1992 in the Bas-Rhin and Haute-Garonne departments, 48% in men and 43% in women were SCD. This event occurred outside hospital in 89% of men and 85% of women. SCD was the first ischaemic symptom in 61% of SCD in men and in 74% of women. Of the SCD occurring outside hospital, 2 to 6% of men and 6 to 7% of women. received emergency treatment in less than 5 minutes. The frequency of SCD increased with age and was highest in men. Between 1985 and 1992, standardised rates (35-64 years) in men fell from 62 to 48/100,000 in the Bas-Rhin (p < 0.01) and from 59 to 36/100,000 in the Haute-Garonne (p < 0.0001); in women, the frequency fell from 17 to 8/100,000 in the Bas-Rhin (p < 0.01) and remained stable in the Haute-Garonne (10/100,000 to 11/100,000). In conclusion, for the first time in France, accurate epidemiological data on SCD is presented, underlying its importance in terms of public health.