The results of a paternity test, unlike some of the medical tests, are pretty easy to understand.

The box contains three sets of cotton swabs to collect cheek samples from the child, the alleged father and the mother. (The mother is optional but helps strengthen the results, the company says.) The swabs are put into separate packets and mailed to Sorenson’s laboratory in Salt Lake City. Results are provided by mail, fax or on a password-protected Web site within five days of the laboratory receiving the samples.

Sorenson said the test was for peace of mind and that the results would probably not stand up in court because questions could be raised about whose samples were submitted. The kit advises people wanting to test for legal purposes to call the company and set up a chain of custody for the samples, which would cost an additional $200.

At least one other genetic test is sold in a drugstore. Sciona sells a $269 service that provides dietary advice based on genetic analysis through Pharmaca Integrative Pharmacy, a chain of 19 stores mainly in California and Colorado.

Rosalynn Gill, chief science officer of Sciona, said that Pharmaca, unlike most pharmacies, had dietitians on staff to help explain the purpose of the test to customers.

“It’s far too early to expect people to walk into a store and buy a genetic test directly off the shelf without some guidance or counsel,” she said. Still, Sciona gets most of its sales from the Internet and from multilevel marketing.

Mr. Fogg of Sorenson said the company now sold about 1,500 to 2,000 paternity tests a month through the Internet and hoped to increase that greatly through sales at drugstores. It hopes to expand to all Rite Aid stores and possibly other chains, he said. It also plans to begin advertising the test in stores, on the radio and possibly on television.

Ashley Flower, a spokeswoman for Rite Aid, would not comment other than to confirm that the kit was being sold in the three West Coast states.

Sorenson, which is bankrolled by a medical device entrepreneur, James LeVoy Sorenson, also offers ancestry testing. Mr. Fogg said he did not know if that test would be offered through drugstores.