The award was presented by the National Gulf War Resources Center, a veterans advocacy group, for Benjamin's reporting on casualties of Operation Iraqi Freedom and problems soldiers have faced since returning.
"Mark Benjamin has saved lives," the group's executive director, Steve Robinson, said in presenting the award Saturday at its annual meeting.
In one story last fall, Benjamin reported that hundreds of sick, wounded and injured U.S. soldiers -- many of whom had served in Iraq -- were being housed in squalid conditions while they waited weeks and sometimes months for treatment.
The reporting led to congressional hearings, and the Pentagon said it was spending another $77 million to make sure that conditions improved.
Benjamin, UPI's investigations editor, also was first to report that a number of mystery illnesses among soldiers in Iraq might be linked to side effects of the controversial anthrax vaccine, and that a number of soldiers with mental problems might have been sent to the war because of inconsistent screening by the military.
Benjamin also has won a Raymond Clapper award, given by the Senate Press Gallery, and the American Legion's Fourth Estate Award for his reporting on the problems.
The gulf war veterans association also gave an Award of Excellence to Army Times reporter Debbie Funk for coverage of military health issues.