Consumers filed nearly 635,000 complaints last year to the Federal Trade Commission, everything from deceptive advertising and bogus gas-saving devices to credit-card scams and identity theft fraud. Although the FTC isn't set up to handle each of those complaints, it does take formal enforcement actions -- such as court-issued restraining orders, asset freezes, civil penalties and transferring cases to the Justice Department for criminal prosecution -- in hundreds of cases annually in which the numbers of victims or dollar amounts are big.

Checking out the FTC's legal actions against scammers and even reputable companies whose practices are unfair offers a heads-up to the kinds of schemes now bilking Americans of millions of dollars. Here are some recent FTC cases:

* Seville Marketing Ltd., a Canadian firm, settled FTC charges that it deceived customers by advertising that its Discreet HIV test kit was 99.4 percent accurate. When tested by the Centers for Disease Control and Prevention, the Discreet results were nearly 60 percent wrong. The settlement, among other restrictions, prohibits Seville from advertising or selling HIV test kits not approved by the U.S. Food and Drug Administration. The FTC is notifying Discreet buyers to contact their doctors.

* The FTC shut down AmeriDebt, a Maryland-based debt counseling service that settled charges in late March that it deceived consumers nationwide by misrepresenting itself as a nonprofit organization and collecting more than $170 million in hidden fees. The firm falsely promised to help consumers get out of debt with no up-front fees but kept voluntary contributions that it said went to creditors. Instead of teaching consumers debt management, as promised, AmeriDebt enrolled them into debt-management plans requiring monthly payments to AmeriDebt, which declared bankruptcy last year. Part of the settlement is a $170 million judgment that the FTC will try to collect through the bankruptcy case. AmeriDebt's victims will be notified of any refunds and can get updates by calling the FTC hotline at 877-862-0886.

* Nabbed in the FTC's "Operation Big Fat Lie" in November, Florida-based weight-loss marketer Femina Inc. settled charges last month that it made misleading claims for its "1-2-3 Reduce Fat," "Siluette [sic] Patch" and "Fat Seltzer Reduce" in Spanish-language ads. The company has agreed to stop making unsubstantiated claims that any product can cause rapid and substantial weight loss in all users without the need to diet or exercise, control metabolism and reduce or eliminate body fat or cellulite.

* NexGen3000.com, an Arizona-based Internet "shopping mall" operation, settled charges last month that it lured consumers through its Web site, live presentations and telemarketing calls and persuaded them to buy into its online shopping malls. Customers paid $185 for a "Basic WebSuite" or $555 for a "Power Pack WebSuite," which contained links to online merchants. NexGen told investors they could earn up to $60,000 a week from commissions on purchases made through their WebSuites. But the NexGen mall was nothing more than an illegal pyramid scheme, says the FTC, and most investors lost money.

* The FTC closed down two resellers of bogus automobile fuel-saving devices last month. The marketers settled charges that they sent illegal spam and made deceptive claims for "Fuel MAX" and "Super FuelMax" -- magnetic devices advertised to improve gas mileage by more than 27 percent and reduce emissions by 43 percent. The Diverse Marketing Group and Net Marketing Group claimed consumers would save $8-$20 per full tank fill-up. The FTC charged the marketers with making false claims for the products, which it says don't work, and with violating the CAN-SPAM Act for inserting names of innocent third parties in the "from" lines and failing to provide a valid physical address in their spam.

Got questions? A consumer complaint? A helpful tip? E-mail details to oldenburgd@washpost.com or write Don Oldenburg, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071.