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The increase in the incidence of prostate cancer in the late 1980s and early 1990s may be partly due to the increased use of prostate-specific antigen (PSA) as a diagnostic test. Prostate cancer is the second cause of cancer death in men and is expected to cause 44,000 deaths in 1995. Researchers at the Mayo Clinic in Rochester, MN compared the use of PSA testing in the community beginning in 1987 with the incidence of prostate cancer. The use of PSA testing increased steadily after 1987, especially in men older than 60. The incidence of prostate cancer more than tripled between 1983 and 1992, from 64 cases per 100,000 to 215 per 100,000. The incidence doubled between 1987 and 1988. The incidence of prostate cancer in many age groups began to decline after 1990, indicating that most of the men with prostate cancer have been diagnosed. PSA testing detected prostate cancer earlier, which could lead to higher survival rates., Objective.--To estimate the incidence of prostate cancer in Olmsted County, Minnesota, from 1983 through 1992 to describe the secular changes that have occurred since the introduction of serum prostate-specific antigen (PSA) testing to the community medical practice in 1987. Design.--Population-based, descriptive epidemiological study with ecologic and individual level comparisons over time. Study Setting.--Olmsted County, Minnesota, where the Rochester Epidemiology Project provides passive surveillance of the population for health outcomes. Subjects.--All 511 biopsy-proven incident cases of adenocarcinoma of the prostate diagnosed from 1983 through 1992. The community inpatient and outpatient medical records of all incident cases were reviewed to evaluate the presenting characteristics of men at the time of diagnosis. Results.--The age-adjusted incidence of biopsy-proven prostate cancer increased from 64 per 1 00 000 person-years in 1983 to 215 per 1 00 000 person-years in 1992. The increase occurred primarily between 1987 and 1988 and was predominately for organ-confined tumors. The age-specific incidence increased dramatically in this same period among men aged 50 years and older. Among men aged 70 years and older, however, prostate carcinoma incidence rates declined after 1990 following the initial increase. This decline among older men contrasted with community-based estimates of PSA utilization rates, which demonstrated consistent increases since 1987 to nearly 50% of the older population in 1992. Conclusion.--These results support the premise that the recent increase in prostate cancer is due in part to the increased utilization of serum PSA testing. Further, the increased incidence appears to be a transient phenomenon due to the depletion of previously undiagnosed cases from the prevalence pool. Finally, these data suggest that, in terms of stage at diagnosis, early detection efforts may be effective in identifying more early stage (smaller) cancers. (JAMA. 1995;274:1445-1449)