During the 1983-85 period, the Belfast MONICA Project registered coronary events in 2,512 individuals (1,913 men and 599 women). The attack rates in men and women per 1,000 person years were 5.9 and 1.7 respectively, and the corresponding mortality rates were 2.4 and 0.61; both rates were heavily age-dependent. There were statistically significant differences in the age and sex-standardised rates for the 107 electoral wards of the Study. The median delay time from onset to delivery of care was 2 hours 30 minutes and 3 hours 2 minutes for men and women, respectively. Delays were shorter in younger and married individuals, and in those with previous infarctions. Unmarried individuals and those with chronic ischaemic heart disease were at significantly increased risk of pre-care death. Sixty per cent of deaths within 28 days of onset occurred before the patient could be admitted to hospital. Sixty-four per cent of males and 67% of females were alive at 28 days. Manual workers and their spouses had a poorer survival at 28 days. Married men and women were at lowest risk of death in the first 28 days, and this could not be attributed to the effects of age.