It was a busy weekend for the Topel family from Chicago: touring the Old City, shopping on Ben Yehuda Street, lounging by the hotel pool and rolling up their sleeves on a Sunday afternoon to give blood at a Magen David Adom drive.

Back up a second, giving blood? "We decided that whenever we came to Israel, we'd donate blood," said Amy Topel, who was here recently to celebrate her twin daughters' bat-mitzvah, together with a group of 25 friends and family from the U.S. "When you give blood in Israel, it's like leaving a part of yourself behind." Donating blood in the Holy Land is also a "bigger mitzvah" than in her hometown, she says. "It's more likely that the blood you donate in Israel will go to another Jew," Steve Topel, her husband, explained.

The Topels, experts say, are part of a growing trend among tourists to Israel, who take in the sights, but make sure to leave a pint of their blood behind in the process. "We're definitely seeing an increase in the number of tourists donating blood while on vacation," said Jonathan Feldstein, the Israel representative of American Friends of Magen David Adom. "But it's not just the number. When I first organized blood drives for tourists in 2006, I had a hard time getting people to participate. Now, people are calling me."

Some 400 tourists gave blood in Israel through organized drives coordinated through the American Friends of Magen David Adom in 2006, which often sets up donation spots in hotels during peak holidays. The number doubled to over 800 the following year and Feldstein anticipates to top 1,500 pints by year's end. About 150 tourists so far have donated through drives he has organized.

"A group called Christian Friends for Israel just called me and they want to organize a blood drive for the 300 people coming here in May," he said. "It's strange, because nowhere else in the world are tourists putting blood drives on their agenda while they are on vacation. I think Israel is unique because it has an emotional and spiritual pull unlike other places. People come out of solidarity, and the feeling that they can do something that saves lives, is personal, and doesn't cost any money really resonates."

Marion Fern, who was visiting from the U.S. recently, agrees. She doesn't usually give blood on vacation, but believes that Israel is an exception. "I was in Prague and Budapest this summer and the thought never crossed my mind," she admitted. "In Israel, though, people are giving their lives, so the least we can do is to give our blood."

Feldstein organizes about 50 blood drives annually for foreigners, often from the comfort of their hotel. The Topel's blood drive, for example, took place in a conference room at the five-star David Citadel Hotel in the capital where they were staying; the hotel provided food and refreshments. Other top hotels like the King David and the Inbal, both in Jerusalem, co-sponsor blood drives regularly as well. Feldstein has also held sessions by the Dead Sea and in Eilat.

"The blood donations from tourists are especially important because they come mostly during the holidays, when there is a shortage," said Eilat Shinar, director of MDA blood services. "Israelis go on vacation, so we are able to supplement our blood supply from foreigners. It has been very helpful."

The apparently growing trend does take some getting used to. "When I heard about the idea of giving blood, I thought it was a little unusual at first, but upon reflection I decided it was a good idea," said Daniel Derman, a U.S. physician who hadn't given blood in 15 years until he rolled up his sleeve while on vacation last week in Jerusalem. "There are very few things we can do as Americans to show solidarity with Israel. We can visit, we can support the economy and we can give blood. These are very tangible ways to make a contribution to the state of Israel."

The numbers remain relatively small, but Feldstein believes the actual rate of blood donations among visitors from abroad is actually much higher. Individual tourists often contact him, and if the American Friends of MDA does not have an organized blood drive specifically for foreigners he sends them to the nearest MDA station to donate. By his own estimates, "for every 10 people who come to us, another two to five go directly to the MDA station."

Still, he acknowledges that the numbers are mostly a "drop in the bucket," compared to MDA's annual blood donations. In 2006, the organization collected 287,500 units of blood, compared to 290,000 units the next year. But by Feldstein's accounting, "we brought in 25 percent of the difference and that is significant."