A lawsuit alleging discrimination based on sexual orientation was filed in Los Angeles Superior Court on behalf of Linda Carlson, who was denied access to eHarmony because she is gay.
Lawyers bringing the action said they believed it was the first lawsuit of its kind against eHarmony, which has long rankled the gay community with its failure to offer a "men seeking men" or "women seeking women" option.
They were seeking to make it a class action lawsuit on behalf of gays and lesbians denied access to the dating service.
eHarmony was founded in 2000 by evangelical Christian Neil Clark Warren and had strong early ties with the influential religious conservative group Focus on the Family.
It has more than 12 million registered users, and heavy television advertising has made it one of the nation's biggest Internet dating sites.
Carlson, who lives in the San Francisco Bay Area, tried to use the site's dating services in February 2007. When she was
"Such outright discrimination is hurtful and disappointing for a business open to the public in this day and age," she said.
eHarmony could not immediately be reached for comment. Commenting in the past on eHarmony's gay and lesbian policy, Warren has said that he does not know the dynamics of same-sex relationships but he expects the principles to be different.
"This lawsuit is about changing the landscape and making a statement out there that gay people, just like heterosexuals, have the right and desire to meet other people with whom they can fall in love," said Carlson's lawyer Todd Schneider.
Carlson's lawyers expect a significant number of gays and lesbians to join the class action, which seeks to force eHarmony to end its policy and unspecified damages for those denied eHarmony services based on their sexual orientation.