Trends in the incidence of and mortality from coronary heart disease during the period 1983-1988 were assessed in the population aged 35-64 years in three areas of Finland. The official mortality statistics and the FINMONICA (Finnish portion of the World Health Organization MONICA (Monitoring of Trends and Determinants in Cardiovascular Disease) project) Acute Myocardial Infarction Register were used as data sources. They both showed that coronary heart disease mortality declined steeply in Finnish men and women. This marked decline in coronary heart disease mortality was associated with a decline in the number of out-of-hospital coronary deaths. The changes in the incidence of acute myocardial infarction in men did not parallel the changes in mortality. No decline in incidence was seen in women in any of the study areas. These results suggest that the routine mortality statistics alone may give an overly favorable picture of coronary heart disease trends. Data on incidence are necessary to assess the need for the treatment and prevention of coronary heart disease.