Here we go again. Another study raises questions about the benefits of mammograms, and another set of confusing statements issue forth from experts.

Last month, Dr. Otis Brawley, the American Cancer Society’s chief medical officer, told The New York Times that the medical profession had exaggerated the benefits of cancer screening.

Then the society said women over 40 should keep having annual mammograms, because seven studies had shown they decreased the risk of breast cancer death. But it also said the test could “miss cancers that need treatment, and in some cases finds disease that does not need treatment.”

So what are women supposed to do? I consulted several experts, all of whom said mammograms were still important. But they differed on who really needed them.

Dr. Laura J. Esserman, a breast surgeon at the University of California, San Francisco, was the author of the report in The Journal of the American Medical Association that touched off the latest debate. She said screening seemed to be good at finding slower-progressing cancers, which probably don’t need treatment, but might not catch the aggressive types early enough. But it also picks up the medium ones, and those are the women who may benefit most.

In her view, women over 70 or 75 need not be screened. She also said evidence was lacking for a benefit in women 40 to 50 unless they have a strong family history of breast cancer before menopause or a mutation in a gene called BRCA. For ages 50 to 70, she said, there is good evidence that screening can reduce the risk of breast cancer death by 20 percent to 30 percent.

Dr. Susan Love, a surgeon and researcher in Santa Monica, Calif., said younger women were less likely to have cancer and tended to have dense breast tissue, so mammograms were more likely to miss tumors. She noted that not all medical groups agreed with the cancer society. Some recommend no screening for women under 50 or over 70.

Some researchers say the benefits of screening far outweigh the risks. Dr. Larry Norton, deputy physician in chief for breast cancer programs at Memorial Sloan-Kettering Cancer Center in Manhattan, said: “The bottom line is that if an individual woman wants to reduce her odds of dying of breast cancer (by at least 24 percent, which is no small effect), then she should follow the current screening guidelines.”