The hazard function provides the instantaneous probability of death (or other key end point) at various times after diagnosis. Unlike the survival curve, the hazard function illustrates graphically or through calculations when deaths are common or uncommon. In this study, hazard functions were derived for prostate cancer by using survival data on large numbers of patients with prostate cancer with data in the Surveillance, Epidemiology and End Results (SEER) database. The results demonstrate a form of prostate cancer that rapidly evolves to cause death within 5 years, and this form of tumor is only partly identified by routine prognostic variables such as serum prostate-specific antigen (PSA) level, histologic grade, and quantity of tumor. The results also validate the presence of a reservoir of nonfatal prostate cancers that have increased rapidly during the PSA era, and they demonstrate that the incidence of fatal prostate cancers has declined.