Hot 100 March Madness 2013: Vote Now in Round 1!

Cast your ballot for the best Top 5 single of the past year.

Last year's Billboard.com Hot 100 March Madness put a twist on the ever-popular college basketball tournament and asked pop fans to vote for their favorite recent No. 1 song on Billboard's Hot 100 chart. Hundreds of thousands of votes were cast, and Britney Spears' "Hold It Against Me" eventually emerged victorious from the field of 32 songs!

At long last, Hot 100 March Madness is back -- with some updated rules for 2013. Instead of pitting the last 32 No. 1 Hot 100 tracks against each other, we've gathered every smash single to grace the Top 5 of the chart over the past year, and placed them in head-to-head match-ups. Over the next month, it'll up to you to vote in the bracket-style tournament and determine which song is the absolute best of these 32 hits!

Check out the full Hot 100 March Madness bracket below, and then support your individual favorites in the first round of voting.

From April 1, 2012 through the most recent charts on March 9, 2013, there have been exactly 32 songs that appeared in the Top 5 of the Hot 100 chart. The match-ups within the bracket were decided arbitrarily, so don't worry about NCAA-style rankings -- any song has a great chance of following "Hold It Against Me" and tasting Hot 100 March Madness glory.

Speaking of Britney Spears, the pop superstar and Will.i.am face a tough Round 1 opponent, as their hit "Scream & Shout" is matched up against One Direction's "What Makes You Beautiful." Other enticing Round 1 battles include Bruno Mars' "Locked Out of Heaven" facing off against Kelly Clarkson's "Stronger (What Doesn't Kill You)"; Nicki Minaj's ubiquitous 2012 hit "Starships" pitted against the recent viral smash (and No. 1 single) "Harlem Shake" by Baauer; PSY trying to topple Katy Perry's "Wide Awake" with "Gangnam Style"; and P!nk's attempt to blow one last kiss to Macklemore & Ryan Lewis, of "Thrift Shop" fame. Some artists, like Justin Bieber, Flo Rida, fun. and Rihanna, have more than one song in play, further increasing their chances of taking home a tournament win!

On Monday (March 11), we'll reveal the 16 songs that won their match-ups and survived the round of 32, and another round of voting will begin. On Thursday, March 28, a new Hot 100 March Madness champion -- the Top 5 song that you think was the No. 1 single of the past year -- will be crowned. Will Britney repeat as champ? Can Carly Rae Jepsen repeat her "Call Me Maybe" magic? And which Justin -- Bieber or Timberlake -- will advance further? It's up to you to decide!

Round 1 of Hot 100 March Madness is now CLOSED! See who moved on and get ready to vote in round 2, launching on Billboard.com Monday afternoon (March 11).