This study from Oppland county, Norway, examines risk factor changes in three regions with different mortality time trends among middle-aged males, for ischaemic heart disease, including sudden, unexpected death (IHD/SUD). The study is partly based on vital statistics and on results from two health screening surveys conducted in 1976-78 and in 1981-83. Regional data for the following risk factors are considered: serum cholesterol, systolic blood pressure, body weight and prevalence of smoking. Risk factor data are from the group of men aged 40-49 years in 1976-78. Changes in risk factor levels from 1976-78 to 1981-83 did not differ substantially between regions with widely different mortality time trends. The north-western, rural part of Oppland county experienced 80% IHD/SUD-mortality increase (95% confidence interval 35%-124%) from 1966-70 to 1981-85, among males aged 40-59. The mean serum cholesterol level dropped by 1.7% (P less than 0.001) from 1976-78 to 1981-83, and the prevalence of smoking was also reduced in this region. The north-western rural region experienced a slightly more pronounced increase in mean body weight and in mean systolic blood pressure, compared to the remaining two regions of Oppland county, where the changes in IHD/SUD mortality were not statistically significant. This study has demonstrated that changes in main risk factors are not necessarily accompanied by contemporary IHD/SUD-mortality changes in the same direction. The explanation could be long time-lags before risk factors affect mortality levels. The results could also indicate the presence of other important risk factors, not evenly distributed between the regions.