The tiny, multicolored cards have shown up all over Washington: scattered on porches and doorsteps, strewn in driveways and placed under car windshield wipers. They promise good times or exotic fantasies. And in minuscule print on the bottom-left corner is the catch.

It will cost $6 to dial certain 976 numbers and hear "Erika Foxx" or "Stacey" whisper your wildest fantasies over the telephone.

The phenomenon, often referred to as dial-a-porn, is not legal in Virginia, but it appears to be flourishing in the District, Maryland and elsewhere across the county. Distribution of the advertising cards is legal as long as they include the price of the phone call, D.C. police say.

But a Chesapeake & Potomac Telephone Co. rule that went into effect in the District today requires all 976 phone messages to notify customers of the cost at the beginning of the telephone call and give them a chance to hang up without being billed. The rule is to go into effect in Maryland this summer.

"Our concern is to make sure that callers know there is a charge for these calls," said Web Chamberlin, spokesman for C&P. The 976 numbers carry a variety of messages, including Dial-a-Prayer, Dial-a-Joke, sports information and horoscopes, and they range from 50 cents to $9.95 a call. C&P is not responsible for the content of the messages, Chamberlin said.

While some District residents have laughed off the lascivious invitations, others have not been pleased with the shower of orange, blue and yellow cards in their neighborhoods.

"I don't appreciate someone grabbing hold of my windshield wiper and putting one of these cards under it like a ticket," said one angry resident of Brandywine Street in American University Park. "And I don't appreciate them sticking the cards where a kid could find them."

Dennis Sobin, a D.C. sex entrepreneur, said he disapproves of the cards because they "create very bad will and hurt business in the long run."

"They border on fraud," Sobin said. "You have to have very good eyesight to see the price. People should be told right up front what the price is going to be."

Sobin also complained about the random distribution of the cards. "They're indiscriminately thrown in public places all over the city, and people under age can get hold of them and make high-cost phone calls."

The Federal Communications Commission wants to prevent minors from being exposed to "a description or depiction of actual or simulated sexual behavior" through the 976 system. According to agency rules, owners of adult message services are prohibited from doing business with minors.

To protect those businesses from catering to minors, the FCC requires that they give out codes for their customers to hear the adult messages, and the firms are prohibited from giving these codes to minors, said Greg Vogt, chief of enforcement for the FCC common carrier bureau.

In addition, the FCC recently issued a rule to allow the firms to distribute decoders, only to adults, for listening to scrambled messages, Vogt said.

C&P shares in the profit from those messages. The message companies buy a line from C&P, the charge for the call shows up on a customer's phone bill, and the profit is split between C&P and the message firm. But the phone company is changing its billing rules for 976 numbers this summer and turning over all the profits to the message firms to encourage more competition, Chamberlin said.