Black men in England are three times more likely than whites to get prostate cancer and tend to be diagnosed five years younger, researchers have found.
Researchers at the University of Bristol found no evidence that black men get poorer access to health care.
They said the differences between races could not be explained by differences in the tests, screening or information black or white men had about the condition.
Reporting in the the British Journal of Cancer, scientists said black men were more likely to be referred to hospital for further investigation by their GP.
Cancer charities said the finding may lead to better care for men at higher risk of the disease.
The study was looking at whether more black men got prostate cancer or just whether they were more likely to be diagnosed.
But hospital records revealed that both black and white men had similar levels of knowledge about prostate cancer, similar symptoms and similar delays before they went to their GP.
Study leader Dr Chris Metcalfe told the BBC: "One of the possibilities based on anecdote was that black men may delay presentation - so the cancer gets to a later stage.
"If anything the evidence showed black men were presenting sooner."
"There's very few known risk factors for prostate cancer but it's starting to look like being of black race is a risk factor."
Dr Joanna Peak, science information officer at Cancer Research UK, told the BBC: "The study indicates that there is a true biological difference between ethnic groups and this knowledge could potentially lead to improved care for men at higher risk of developing prostate cancer."