The decline in ischemic heart disease (IHD) mortality in the United States in recent years is thought to have contributed to increases in cancer mortality. To estimate the interrelation between these competing causes of death between 1970 and 1988, I constructed a hypothetical population schedule by assuming that age-specific IHD mortality risks had not declined. The difference between the actual population and the hypothetical population represents persons who did not die from IHD and were thus available to die from cancer. Using observed age-specific cancer risks over the entire interval, 153,207 of the 7,649,058 cancer deaths (2.0%) in persons age 20–85 years occurred in IHD survivors; in 1988, 24,053 of the 482,490 cancer deaths (5.0%) occurred in IHD survivors. Among 55 to 85 year olds in 1988, IHD survivors accounted for 5.5% of the cancer deaths. Alternative assumptions about the susceptibility of IHD survivors to cancer have little impact on the contribution of IHD survivors to cancer deaths. Results from a separate analysis demonstrated that the proportional contribution of true cancer risk to the increase in cancer cases tripled in the interval 1970–1988 compared with the interval 1930–1970. These observations indicate that the contribution of the IHD mortality decline to the increase in cancer mortality has been small and does not account for the increasing age-specific risks for cancer among older persons.