MD.45 was a side project put together by Megadeth's guitarist/frontman Dave Mustaine ,Fear's Lee Ving on singing duties, bassist Kelly LeMieux and former Alice Cooper member Jimmy DeGrasso on drums. Dave Mustaine, fed up with Megadeth at the time, but still interested in music, wanted to create an album showcasing a different musical style than Megadeth.
According to an answer given on the Megadeth website, "Mustaine and Ving created the band name by reversing their initials. .
