The American Cancer Society on Thursday issued new guidelines recommending that all men ages 50 to 69 undergo prostate cancer screening using a blood test every two years.

Black men and those with a strong family history of prostate cancer should start annual screening at 45, the guidelines said.

Universal screening for prostate cancer, which accounts for about 2.5 percent of all deaths among U.S. men, has long been a subject of controversy. The evidence of the benefits of regular testing of blood levels of prostate specific antigen, or P.S.A., is somewhat limited. And there are well-documented harms associated with diagnosing and treating all prostate cancers, which are typically slow growing and may not ever cause issues in men who have them.

The new guidelines diverge from earlier recommendations that patients and physicians decide together about screening, based on careful consideration of the risks and benefits and patients’ values.

“This is truly a reversal,” said Dr. Philipp Dahm, a professor of urology at the University of Minnesota who was not involved in the guidelines.

The A.C.S. said it was updating its guidance based on new evidence and changes in how doctors monitor and treat prostate cancers.