Volunteer vacations can be thought of as short-term versions of the Peace Corps, which was the model for the first service-oriented travel programs. Although there are no precise data on volunteer travel, people in the industry and those who study it say the sector grew slowly but steadily in the 1970s and 1980s, then took off in the 1990s.
''It is definitely a growing part of the travel industry, and it has grown relatively quickly," said Doug Cutchins, director of social commitment at Grinnell College in Iowa and coauthor of ''Volunteer Vacations: Short-term Adventures That Will Benefit You and Others" (Chicago Review Press).
Service-oriented travel was one of the first segments of the travel industry to bounce back after Sept. 11, according to Cutchins. He said it got a boost from President Bush's call for Americans to dedicate two years of their lives to public service.
The rise of service-oriented tourism parallels that of eco-tourism, and both are, in part, responses to concerns that conventional tourism sometimes harms the cultures, economies, and environments of developing countries. Travelers who choose volunteer tourism have a variety of motives. Some have a sense of moral duty; others see it as part of a religious commitment. Many programs are affiliated with religious groups.
''Some people say, 'This is how I show my love for the Lord,' " said researcher Michael Ray Smith, who conducted extensive interviews with the service-oriented group Baptist Men of North Carolina. The organization's volunteers respond to disasters around the world and help with rebuilding.
''Then you have the people who say they do it to see the looks on people's faces," said Smith, who teaches mass communications at Campbell University near Raleigh. ''And you have other people who say, 'I do it because I think I'm supposed to do it. It's something I can do.' "
