Women should not let fear of pain deter them from being screened for breast cancer, researchers say.
Some women are deterred from being screened
Experts say some are put off from having the potentially life-saving scan because they are worried it will hurt.
But US researchers have found the pain is relatively mild - slightly less than that created by a mild headache or tight shoes.
UK experts say women should be reassured by the research and ensure they attend for their regular scans.
Researchers from Wake Forest University Baptist Medical Center talked to 200 women straight after they had been given a mammogram.
This study should encourage and reassure all women in the UK who are due to be screened
Delyth Morgan, Breakthrough Breast Cancer
Almost three quarters said they had felt some pain.
On average, they reported the pain as registering at around four, on a scale of one to 10 with 0 being "no pain at all," 5 being "about average, like a mild headache or shoes that are a bit tight" and 10 being "the worst pain you've ever felt."
Pain levels were not associated with age, race, education, breast size, body mass index, or having another medical problem.
Even women who said they were sensitive to pain did not report higher pain levels than other women.
But pain was higher if the screening occured within eight to 14 days of their period.
Women said the most stressful part of a mammogram was waiting for the results, ahead of having the actual test.
The researchers said informing women of the low numbers of mammograms that lead to a diagnosis of cancer - around five in every 1,000 - was the best way to reduce their stress.
Penny Sharp, associate professor of family medicine, who led the research, said: "Physicians and patients have reported that concerns about pain are a major barrier for women getting screening mammograms.
"Our study suggests that the actual pain experienced is relatively low.
"In fact, the level of pain would not deter 94% of the women from returning for mammography screening."
She added: "Mammography is an important tool for breast cancer screening, so removing any barriers to women receiving these tests is important.
"Women who are particularly concerned about potential pain may benefit from learning about these study results."
Delyth Morgan, chief executive of Breakthrough Breast Cancer told BBC News Online: "Early detection and diagnosis are vital in improving a woman's chances of survival and the NHS screening program is the most effective way of ensuring this, with 9,500 cases detected each year.
"Almost half of these cancers are too small to be felt by the hand and, if not for screening, may not be detected until a much later stage.
"This study should encourage and reassure all women in the UK who are due to be screened, that the benefits of screening far outweigh any discomfort or mild pain they might experience during a mammogram and should not deter them from keeping their appointments."
The research is published in the Archives of Internal Medicine.