An international comparison of mortality rates in middle-aged men (35--54 years) from cardiovascular diseases (CVD) during the period 1970--1974 was made. The material for this study was obtained from the statistics of the WHO (World Health Statist. Ann. 1970--1974, Vol. I, Vital Statistics of Causes of Death. WHO, Geneva, 1973--1976). The mean death rate of middle-aged men from all CVD and ischaemic heart diseases was clearly higher in Finland than in any other country in the world during the 5-year period. The mortality rates according to all ICD (International Classification of Diseases) main groups of diseases were determined for a selected group of countries containing all the Scandinavian countries, the United States, Canada, Hungary, Australia, Scotland, and Czechoslovakia. The death rates of all natural (ICSI-XVI) and unnatural causes (ICDXVII) were higher in Finland than in the other selected countries. Also the proportion of cardiovascular deaths as a percentage of all natural deaths was clearly higher in Finland than in any of the above countries, whereas in these countries proportionally more deaths were due to neoplasms than in Finland, especially in men aged 35--44. Only in Hungary did infectious diseases account for about 4.5% of all natural deaths; in the other countries they accounted for only about 1--2%. In the United States, Sweden, Czechoslovakia and Canada a clearly higher relative number of deaths (about 9--13%) were due to diseases of the digestive system than in the other countries (about 3--9%), whereas the relative numbers of deaths from respiratory and genitourinary diseases were uniform among all selected countries. Only in Denmark and Norway was a prominent proportion of the deceased (3.5--9.5%) certified as having died due to some symptom or ill-defined condition. About 90% of all middle-aged men died in each country from various diseases of the above six main ICD categories. As a whole, the above single deviations from the general trend were so small that the present results do not support the view that the differences in certifying and coding practices could explain the significant differences found in cardiovascular mortality of middle-aged men between various countries.