Anyone claiming the Harvard-Yale rivalry is overstated needed only to look at the line of students in Loker Commons yesterday, poised to spill their blood for a Harvard victory—literally.

Volunteers flocked to donate their Crimson blood on the first day of the Harvard-Yale Blood Drive Challenge. The event pits the two schools against each other in three categories—total production units of blood, the number of first time donors, and the number of volunteer staff. The points earned in each category will be added up to determine whether Harvard or Yale triumphs this year. All blood donations will go to the American Red Cross.

Although participants were in a celebratory mood, the cloud of last year’s loss to Yale hovered over the event. In 2005, Yale collected 60 more units of blood than Harvard.

But Harvard’s blood drive staffers questioned the legitimacy of Yale’s victory.

“Yale ran a 22-hour blood drive last year,” Kathy M. Goodson ’07, one of the drive’s coordinators, said. “Ours only ran for 18 hours. We realized later that this time difference wasn’t taken into account in the scoring.”

The contest judges will factor time differences into the scoring this year, Goodson said.

Though the drive extends through Friday, there are signs of a Crimson victory on the horizon.

“We have a very good shot,” Tali Mazor ’07, another blood drive coordinator, said. “People have been showing up.”

As a consequence of last year’s loss, Harvard had to place an ad in the Yale Daily News, congratulating the Bulldogs on their victory. This year the stakes are perhaps even higher—the losing school’s dean must don the victorious school’s apparel for a photo, also likely to run in the paper. But Dean of the College Benedict H. Gross ’71 wrote in an e-mail that he is not worried that he will have to display the Bulldogs’ colors.

“I’ve been assured that we won’t lose,” Gross wrote. “So there is nothing to worry about.”

Dean of Yale College Peter Salovey has a slightly different take.

“I know Dean Gross, and I think he would look spectacular in blue...We will avenge our triple over-time football loss...with blood!” Salovey wrote in an e-mail.

Organizers emphasized the Harvard-Yale rivalry in promoting this year’s drive, Goodson said. But Goodson and Mazor said they believed participants were motivated by an understanding that the Red Cross needs their blood.

Goodson said blood donations are especially important right now.

“Particularly in the winter, a lot of drives get snowed out. This diminishes the supply,” she said. “At the same time, there is an increased number of car accidents, so the need is greater.”

The blood supply is perishable, Mazor noted, and must be continually replaced.

“You can’t just build up a stock,” she said.

Last year, Harvard collected 250 units of blood. According to the Red Cross website, over 14 million units of blood are needed in America each year.

The Yale blood drive ran earlier this month, but Yale’s drive organizers have not yet divulged the results. Goodson said the Harvard and Yale groups will likely determine the winner later this week.

­—Staff writer Jillian M. Bunting can be reached at jbunting@fas.harvard.edu.