Edinburgh and Glasgow are the two largest cities in Scotland, which has one of the highest coronary heart disease mortality rates in the world. Within Scotland, there is a geographical variation in these rates and Glasgow has a higher mortality rate than Edinburgh. However, the cities also differ socially and economically. Population surveys have been conducted in centres in both Edinburgh and North Glasgow using the MONICA project methods. These surveys were performed simultaneously in 1986 in men and women aged 25-64 years. Preliminary analysis shows that the differences in cigarette smoking, blood pressure and body mass index in men and women between the two centres are consistent with the difference in cardiovascular mortality. However there is no difference between the centres in reported exercise levels, and the difference in mean serum total cholesterol between the centres is in the opposite direction to that expected. Possible explanations of these differences are discussed.