An estimated 50 women are raped every hour in the Democratic Republic of Congo.
A study in the American Journal of Public Health has found that 400,000 females aged 15-49 were raped over a 12-month period in 2006 - 2007.
The BBC says the rate is significantly higher than the previous estimate of 16,000 rapes reported in one year by the United Nations.
The Congolese government says the perceived increase in sexual violence is the result of better opportunities for victims to report rape.
The DRC has been plagued by decades of war, with rape often used as a weapon in eastern DR Congo.
The study used data from a government health survey in 2007.
Previous estimates were derived from police and health centre reports.
The highest numbers of rapes were found in North Kivu, where an average of 67 women out of 1000 have been raped at least once.
However, the report said sexual violence was widespread outside the conflict zones of eastern Congo.