The card mailed to home owners in two Prince George's County communities reads: "One Phone Call Can Sell Your Home . . . Keep This Card in Case of An: EMERGENCY . . . WE PAY CASH FOR HOUSES."

Residents of Riverdale and Riverdale Heights, predominantly white neighborhoods that adjoin each other, say they have been receiving mail solicitations - such as the card mailed by a Cheverly real estate firm - as well as phone calls from realtors in increasing numbers over the last few months.

The solicitations began, the residents say, after the all-white Riverdale Baptist Church moved to Largo and sold its old building at 6200 Riverdale Rd. to Refreshing Spring Church of God in Christ, a black congregation formerly located in Washington.

The new church in the old neighborhood, the mailings by realtors, plus allegations of "racial steering" (realtors showing houses only to blacks in this case) have made many white Riverdale residents feel unsure of their future in one of the Washington area's few remaining enclaves of moderately priced homes.

"We've been told by the realtors we're in a neighborhood, that's going to go all black," said Hilda Utermohle, a white Riverdale resident who is leading a citizen counter-attack on the realtors.

Riverdale and Riverdale Heights are old communities consisting of a mixture of Victorian frame houses, small bungalows, suburban subdivisions and apartment complexes. It is an area where homes can still be bought in the $30,000-to-$40,000 price range.

At the time of 1970 census, there were nearly 20,000 residents and only 3 per cent of them black. The few black residents have been at times the target of white hositility.In 1969, for instance, a homemade firebomb was tossed into the home of the first black resident of a section near East-West Highway. This year, there was a cross-burning in the old Erco Field in Riverdale, a reminder of persistent racial antagonisms in the communities.

While Riverdale has remained predominantly white, the overall black population of Prince George's County has in recent years increased rapidly to 25 per cent. Some communities inside the Beltways have become largely black in the process as families from Washington have moved to better housing in the suburbs.

The tensions and fears that often accompany such demogrpahic shifts were evident the other evening in the auditorium of St. Bernards School, 5811 Riverdale Rd., where 100 residents, virtually all white and many middle-aged and older, gathered to express dismay and demand action.

Present were County Human Relations Commission Chairman Dervery Lomax; Paul Fowler, executive vice-president of the Prince George's Board of Realtors; and John Lally, aide to county executive Winfield M. Kelly, Jr., who, in a letter distributed at the meeting, expressed his concern over allegedly "questionable practicers . . . whereby residents are posibbly being induced to sell their homes below market value, disturbing the economic viability of your community."

Representatives of four realty firms alledgely engaged in bulk mail solicitation were invited. There were empty chairs by the place names of Federal Real Estate, J.M. Hall and Pride-Mark Properties.

Dan Johnson, manager of Pride-Mark, explained later that his firm was out of town. "We've been in business for 12 years, and we've always got a lot of business from what that area," he said. "We don't want to do the first thing in the world to have problems."

The firm's mailings, he said, are not targeted to one area and contain no hard sell. Repeated efforts to reach the other realtors were unsuccessful.

Kenneth Woodring Jr. was there, however, as president of Prince George's Properties and president-elect of the county realtors' board. His firm, he said, is now doing only 5 per cent of the mail solicitation it did five years ago. Nonetheless, he said, his firm would cease all mail and phone solicitation "if it would help set the community's mind at ease."

There are more "FOR Sale" signs in Potomac than Riverdate, he told his listeners. The 72 homes for sale in the Riverdale area at present did not constitute "an alarming number." he added.

Under the law passed by the Country Council in 1972, sale solicitations are allowed if "limited to random and isolated inquires not of systemic design to cover a substantial section of any neigborhood." To date, there have been no prosecutions under the law.

Lally, Kelly's aide, and Human Relation's Lomax promised to investigate and take action where residents could had been violated.

"I was around when we never had see opportunity in Prince George's to see the the horses." said Lomax, a former mayor of College Park who is black. "There are methods of improper block-busting. We want right to prevail."

"There are economic fears and racial fears," lectured Lally. "We're not going to prevent anyone from moving into a neighborhood if they can afford it. That's America. Sorry . . . If it's a racial issue, if you just don't happen to like certain people, that's not protected under the law."

"This is fry your friendly relator night," began Fowler, the county realtors board executive.

"Let's address the real issue, the fears," Fowler said. "It's a free country, ladies and gentlemens, and if you've got the income, you are entitled to purchase a home that is for sale . . . It's a changing world, it's a changing community, and we have to live with it . . . These people, blacks, are people, too. They aren't any different than you. They have the same concerns as you."

Utermohle, who was moderating the meeting, insisted the problem was not racism by residents but scare tactics by relators.

"Solicitation," said a leaflet handed out at the meeting , is indicative of how the community is viewed by the real estate industry. If the real estate industry views a community as one in change, they make increased efforts at soliciting for sales.

"This can often have the effect of a self-fulfilling prosphesy." The increased solicitation can act to panic residents into selling their homes. For this reason, unchecked solicitation is dangerous to the continued intergrity and stability of the communtiy." the leaflet said.

"If you want your neighborhood to stay the way it is, don't sell. You have to hang onto what you have." said Jack Queen, who moved from Anacostia to Cheverly 10 years ago. "We were one of the last three white families to leave our area. My property values didn't go down."

A man who, with his wife, were the only black Riverdale residents present, came forward from the back of the auditorium. His name was Ronald Widly. He was 32, an art teacher at Mount Rainier Junior High who had moved to Riverdale nine years ago.

"What I see here tonight," he began, "is the fear of black people coming in." His voice was not angry but soft-spoken and there was no other sound in the room.

"I see fear in your eyes. There's no use in fearing us because we're all around you, and we're going to be all around you as long as there is a Washington, D.C.." Wildy said.

"Please dismiss your fears because we want no more than to live in a clean, wholesome neighborhood," he said.

His message, the last of the eveningwas greeted with loud applause.