The following is quoted from Frequently Asked Questions at
The Official U.S. Government Site for People with Medicare
"What happens if I choose not to join a Medicare drug plan by May 15, 2006? Can I join later?
If you donít join a plan by May 15, 2006, and you donít currently have a drug plan that, on average, covers at least as much as standard Medicare prescription drug coverage, you will have to wait until November 15, 2006 to join. When you do join, your premium cost will go up at least 1% per month for every month that you wait to join. Like other insurance, you will have to pay this penalty as long as you have Medicare prescription drug coverage.
If you join after May 15, 2006, the next open enrollment period is November 15, 2006 to December 31, 2006. However, coverage for people who enroll during this period will not take effect until January 1, 2007."