Studies have shown that the decrease in ischemic heart disease mortality over the past decades was paralleled by an increase in socioeconomic disparities. Using two large Swedish cohorts defined in 1986 and 1996, the authors examined whether the effect of neighborhood socioeconomic position on ischemic heart disease mortality strengthened over the period and whether the relative contribution of individual and neighborhood socioeconomic effects changed over time. Multilevel survival models adjusted for individual factors indicated that neighborhood socioeconomic effects on ischemic heart disease mortality increased markedly between the two periods (hazard ratios for residing in the most vs. least deprived neighborhoods were 1.60 (95% credible interval: 1.36, 1.89) for the 1986 cohort and 2.54 (95% credible interval: 1.99, 3.21) for the 1996 cohort). Comparing the neighborhood socioeconomic effect with the strongly predictive effect of 15-year individual income indicated that the neighborhood effect was two times weaker than the individual effect in the 1986 cohort (-48%, 95% credible interval: -22%, -68%) but of comparable magnitude in the 1996 cohort (-11%, 95% credible interval: -42%, 29%). This increase in the contribution of neighborhood factors to the socioeconomic gradient in ischemic heart disease urges investigation into the exact mechanisms between the residential context and coronary health.