Although survival rates are useful for monitoring progress in the early detection and treatment of cancer and are of particular interest to patients with new diagnoses, there are limited population-based estimates of long-term survival rates. We used data collected by the Surveillance, Epidemiology, and End Results Program for cases diagnosed during 1974-1991 and followed through 1992 to estimate relative survival at 5, 10, and 15 years after diagnosis of cancer of the breast, prostate, colon and rectum, and lung. Relative survival after diagnosis of breast and prostate cancer continued to decline up through 15 years after diagnosis, whereas survival after diagnosis of lung and colon or rectal cancer remained approximately constant after 5 and 10 years, respectively. Age-specific patterns of survival varied by site, stage, and demographics. Among patients with localized breast and prostate cancer, women who were younger than age 45 at breast cancer diagnosis and men who were 75 years and older at prostate cancer diagnosis had the poorest relative survival. Relative survival among lung cancer patients decreased with age at diagnosis, regardless of stage or demographics, and age-specific patterns of relative survival for patients with cancer of the colon and rectum differed according to race. Among white patients diagnosed with cancers of the colon and rectum, relative survival did not vary by age at diagnosis; among black patients older than 45 at diagnosis, relative survival decreased with age. This study provides population-based estimates of long-term survival and confirms black/white, male/female, and stage- and age-specific differences for the major cancers.