Rene Pengra, 36, thought she'd met her match on Yahoo! Personals. The guy sounded intelligent and introduced himself as a philosophy professor at the University of Michigan. But she grew suspicious when his name didn't show up on the school's Web site. (He also claimed to be the only man alive to have been bitten by a shark and struck by lightning.) When he asked her out, Pengra--a lawyer--ran a background check. "It turns out he was still married, he wasn't a philosophy professor and he'd lied about his age," she says.

If you've surfed the Net for love, you know that losers are easy to come by. But along with the harmless fibbers and philanderers can come dangerous creeps and felons. How do you separate the Romeos from the Pinocchios? Many of the larger dating sites are acknowledging the problem. drops 2,000 of its 12 million members a month, mostly from reports of "unwelcomed and inappropriate" communication, says the site's president, Tim Sullivan. But as online dating gets more competitive, a number of upstart sites are trying to woo would-be daters by claiming they can weed out losers. In most cases, the sites use voluntary background checks: customers submit to a database search with the understanding that other members will do the same., which launched in November, makes subscribers agree to a check at registration. After screening members' names against criminal records from county and state registries, the site has dumped about 10 percent of its 300,000 members. Several of the major online dating sites are beefing up security, too. and Spring Street Networks, which powers AOL's, are expected to roll out optional background checks by the end of the year.

Some sites use icons to show what different users have had checked. At, members can have their own age, gender and location verified., an identity-check company, is working with dating sites to allow members to provide confirmations of their living situation, work history and income level.

Sites like rely on testimonials from pals to help screen out weirdos (hardly a foolproof system, as anyone who's been fixed up on blind dates can attest). Last month the site revamped its account settings so users can restrict or expand the number of people who can contact them., founded by Elle columnist E. Jean Carroll, asks women to post photos of eligible bachelors in their lives and then rave about them. If you have doubts, you can check references. Jeff Miller, who was once spooked when an online date let herself into his house, found love on the site when Kristi Spann, 35, logged on. The reference feature, she said, made her feel safe. Now they're planning a May wedding.