Market Research firm NDP reported that iTunes has past Wal-Mart in music sales in both January and February, if using 12 downloads as a standard equivalent of a CD.
iTunes has sold more than 4 billion songs since its launch in 2003, with more than 50 million customers having used the service.
Eddy Cue, iTunes VP, said that he was "thrilled " by the findings in the survey.
As Bob Dylan once sang, 'the times they are a changing'.