BACKGROUND: The level of mortality from cardiovascular disease (CVD), coronary heart disease (CHD) and from all causes varies considerably within Oslo. The purpose of this study was to examine these differences according to cardiovascular risk factors and socioeconomic variables at the district level. METHODS: Total mortality rates and cardiovascular mortality rates for subjects aged 45-74 years in 1991-1995, and their relationship to cardiovascular risk factors and socioeconomic indicators in the 25 districts of Oslo were studied. Cardiovascular risk factors were based on data from 40 year olds in 1985-1988. The following variables were used as independent variables in the regression analyses to explain differences between the districts: daily smoking, cholesterol level, systolic blood pressure, education and income. RESULTS: Mortality rates were strongly related to cardiovascular risk factors and to socio-economic indicators, with correlation coefficients (Pearson) of 0.74 for smoking and CVD mortality, and -0.78 for high income and CHD mortality. Smoking explained 70% of the differences in mortality from all causes for men and 46% for women, and 61% and 49% of the differences in CVD mortality for men and women respectively. Diastolic blood pressure and total cholesterol were closely related to socioeconomic indicators and to smoking, but the relative strength of the cardiovascular risk factors in the multivariate analyses differed for males and females. CONCLUSION: diovascular risk factors and socioeconomic indicators at the population level were strongly related to mortality, and explained a large proportion of the differences in mortality between different districts of Oslo in the 1990s.