The coronary heart disease (CHD) mortality rates for men aged 35–44 years decreased by 25% from 1966–70 to 1976–80. In older age groups only a modest decline was observed. The decrease in CHD mortality is probably due to a decrease in incidence. The reason for the decline is not known, but some changes in health-related behaviour have occurred in Norway, probably already starting in the 1960s. There was an increase in meat, sugar and total fat consumption and a decrease in the intake of cereals both before and after the Second World War. These trends seem to have slowed down and in a recent survey 44% of the population reported changes towards a low fat diet. The percentage of non-smokers is increasing, particularly since 1975–76. Physical activity in leisure time has increased since the mid-70s but there are social gradients with the most active subjects being recruited from the higher social strata. The improved medical care of CHD patients is not thought to have had a major impact upon the decline in the mortality rates. The most probable explanation for the changes is an increase of non-smokers and a turn towards a less coronary prone diet.