For years, Art Thomas sifted through the stories and rumors traded among relatives and he wondered: Exactly where did I come from?

Last fall, Thomas, a retired information technology manager in Springfield, Ohio, turned to his body for answers. He scraped a cell sample from inside his cheek, mailed the swab to a test lab and waited for science to supplement his extensive genealogical research.

Thomas' quest to unlock the secrets of his own DNA is far from a solitary one. A small, but fast-growing number of consumers are paying for a proliferation of partly self-administered genetic tests, hoping to determine everything from paternity to their propensity to develop certain diseases to their own ancestry.

Some health-related tests have stirred skepticism among doctors and geneticists concerned about their validity and consumers' ability to interpret the results. But more consumers are proceeding with such tests to satisfy their curiosity, and marketers are responding.

Discount retailer Target Corp. now sells DNA collection and profile kits online. Some specialty drug stores have begun stocking DNA-based nutritional tests. Ancestry tests have taken on new prominence with a project by the National Geographic Society.

The increased marketing of self-administered DNA testing is most evident on the Internet, where numerous companies offer an array of products. It's hard to know how many consumers are taking these companies up on their offers, but public interest is clearly growing, observers say.

"People are curious," said Kelly Ormond, associate professor at Northwestern University and past president of the National Society of Genetic Counselors. "I think, in general, many people take the approach that if I could know about my health or something in my family, I'd like to know."

The many tests available serve very different purposes. But some see a commonality in their appeal, finding an audience with consumers who have gradually come to see genetics as less overwhelming and potentially useful.

There "has been an increasing expectation of what this technology would be able to deliver," said Rosalynn Gill-Garrison, a co-founder and chief science officer for Sciona Inc., which sells a line of tests designed to help people match their diet with their genetic predisposition. "Now, have we met all those expectations? I don't think so. But certainly people are very interested in wanting to use this technology to learn more about themselves."

The business of marketing DNA testing to the public barely existed a decade ago. Awareness has increased greatly since the 2003 completion of the Human Genome Project, an effort by the federal government to map DNA.

Some types of tests have attracted new interest, like those featured in a recent television show on the Public Broadcasting Service that traced the ancestry of Oprah Winfrey and other black celebrities.

Consumers who have purchased some of the tests see the decision in very personal terms.

For the past 15 years, Thomas has poured his free time in to researching his family tree. But Thomas, who is black, remained uncertain about pieces of the family legend that said both a great-grandmother and a great-grandfather were white.

He studied a faded photo of a family reunion, taken in 1920, that shows five rows of relatives, noting that some of his predecessor were, indeed, much lighter in complexion than others.

Thomas, whose undergraduate degree is in biology, knew something about genetics. So he spent just under $300 for a package of two tests from Family Tree DNA, owned by Genealogy by Genetics, Ltd., and $175 for a test marketed by Ancestry by DNA, owned by DNA Print Genomics Inc.

The results arrived in the mail about a month later, confirming and amplifying Thomas' earlier findings that his family tree includes some white ancestors. In fact, the test showed, his genetic makeup was 49 percent European origin, 48 percent African and 3 percent Native American.

"It confirms a lot of oral history," Thomas says.