GMAC has recently instituted a policy to curb rampant repeat test-taking. In order for an individual to test more than five times, a written request must be submitted to GMAC. Only after permission is granted is that individual allowed to test beyond five times. A research study aimed at greater understanding repeat test-taking will commence in the fall of 2002.
-------Extracted from GMAC.com ( FAQs)
I do recommend test participants to pay attention to the changing policy of GMAT.