Marriott Rewards members who make two paid stays between Feb. 1 and April 30, 2012, will earn a free night to use for a future stay at category 1-4 hotels worldwide. A maximum of only two free nights can be earned during the promotion (after four paid stays). The free award nights you earn with the promotion must be used by Sept. 30, 2012.
You must register for the promotion by March 31, 2012. All stays made after Feb. 1 will count as long as you register by March 31.
Bottom line: This is another recurring promotion from Marriott Rewards and the program ran a similar promotion between Sept. 15, 2011 and Jan. 15, 2012, but with that promotion, members were required to use a Visa card. This promotion has no stipulation about how you pay for the hotel stays.