Ischaemic heart disease among men in Norway during the period 1966-1985: two counties with different mortality time trends. We have examined regional differences in mortality from ischaemic heart disease, including sudden, unexpected death (IHD/SUD), among Norwegian men aged 30-69 years, during the period 1966-1985. Mortality time trends were considered. The two counties with the most widely differing IHD/SUD mortality time trends were Rogaland and Oppland. Rogaland, located in south-western Norway, experienced a 24.1% IHD/SUD mortality rate decrease between 1966-1970 and 1981-1985, while Oppland, in central south-eastern Norway, experienced a mortality rate increase of 12.4%. Marked regional differences within these counties were found. The highest IHD/SUD mortality rate increase occurred in rural areas of Oppland. Urban areas of Rogaland had sharply decreasing rates. Knowledge of such regional mortality differences could provide useful information regarding aetiological factors and serve as a basis for preventive measures and health-care planning. 