When Kathe Allen moved to Washington from Georgia, she gave up a two-bedroom, two-bath, fully carpeted apartment with a fireplace, balcony and drapes. The rent was $235 a month.

She and her husband Olin wanted an apartment convenient to both their jobs -- she is a graduate assistant at the University of Maryland and he is a naturalist with the Fairfax County Park Authority. Middle ground was either in the Bethesda area of Montgomery County or near Suitland in Prince George's County.

"We were thinking of renting in Montgomery County, but the rents were so high we couldn't find anything that we could afford," said the 27-year-old Allen, who is teaching a course in career development while studying for a master's degree. "So we just drove along the Beltway and got off at every Prince George's interchange between College Park and Fairfax. We literally stumbled upon the complex -- Holly Hill Apartments -- and we really like it."

For $347 a month the Allens have a two-bedroom, one-bath garden apartment in Forestville, just inside the Beltway near Andrews Air Force Base. It does not have a fireplace or come with drapes, but for the Washington area, it has one of the most reasonable rentals around.

A report to Congress in 1979 said the slump in construction and the trend to condominium conversions had created a crisis in the rental housing market. That 35 percent of American families who lived in apartments faced the lowest vacancy rate ever, it said.

But Prince George's County is an exception. Apartments comprise nearly 50 percent of its housing, as a result of a building boom in the 1960s that added 50,000 garden apartments to the landscape.

The availablity of rentals has attracted young couples like the Allens, with a joint salary of slightly more than $20,000, as well as moderate to low-income renters, many of whom have moved from downtown Washington. Prince George's now has the largest number of rent-subsidzed tenants -- about 7,000 -- in the Washington suburbs.

"In the 1960s, Prince George's County was proud that it was the fastest-growing county in the country. They were building one garden apartment after another," said Earl Morgan, head of the County Housing Authority. "Now people are beginning to take another look at the rentals because they don't bring as stable a population."

The proposed revision of the General Plan for the county calls for a reversal of the housing pattern -- by giving priority to single-family rather than multifamily zoning, and by encouraging home ownership through tax and financing incentives. The new planning goal is that by the year 2000, Prince George's housing would be composed of 65 percent single-family dwellings and 35 percent rentals.

The county now has 90,000 apartments and a vacancy rate of between 5 and 6 percent, slightly above the national average of 5 percent and significantly higher than in other Washington suburbs. In Montgomery County, fewer than 3 percent of the apartments are vacant at the end of the month.

The large number of rentals has attracted a mobile population that has posed special problems for schools and the local government.

Elementary schools in Prince George's have an average transfer rate of 42 percent, meaning that during an academic year, 42 percent of the elementary students change schools or enter or leave the system. In some schools the turnover is as high as 60 percent. That compares with an average of 19 percent in Montgomery County.

To ease the disruption, school officials are trying to standardize the curriculum so that the same courses, textbooks and lesson plans are used in every school.

"The turnover has an effect on teacher morale," said Brian J. Porter, spokesman for the Prince George's public schools. "It's frustrating to begin a year with a glimmer of hope, start to see some benefits and -- poof, the student's gone. Or to be in the middle of the year, having a whole class developing some terrific goals, and in come three students who weren't there in the beginning of the year. It plays havoc with an educational program and with achievement tests."

Rentals affect the county's tax base as well, since single-family homes account for 70 percent of the property tax revenues, and apartment owners pay only 11 percent.

The county levied an occupant tax on apartment renters in fiscal years 1976 and 1977, but it was criticized widely and repealed after two years.

While other jurisdictions are trying to discourage or slow down the rate of conversions through tax laws and requirements that tenants associations be given the right of first refusal in the sale of a buidling, Prince George's welcomes condominiums.

"We're trying to head more toward having people purchase units and leave the rentals behind," said Morgan. "As other areas run out of condominiums, people will begin to look at Prince George's."

About 5,800 apartments were converted to condominiums through last July, half as many as in Montgomery County, although Prince George's has twice as many apartments.

The number of conversions in the last four months, however, was greater than the total in the last four years, according to one county official, and more are expected. County officials believe many of the buyers come from other areas to purchase the relatively low-price units as investments.

"In Prince George's you've got a receptive government, you can buy buildings for a song, and create units which sell for $35,000. That's the next fertile ground for condo conversions," said John O'Neill, vice president of the Apartment and Office Building Association whose 1,000 members own 250,000 apartments and 30 million square feet of office space in the Washington area.

Until the county succeeds in reshaping its housing patterns, the availability of apartments will continue to attract people like Nancy Grinberg, 26, who grew up in Chevy Chase, lived in a group house in Rockville for a year, then married and moved into an apartment in the complex where the Allens live.

"My friends from high school are either renting group houses or married and living in Frederick," she said. "I don't know any who are living by themselves."

"Within a couple of years, if we're lucky enough and if a miracle happens, maybe we'll be able a buy a house," said her husband Rick, who works for the Fairfax County Park Authority. "I'm hoping we can save money because there's just the two of us and the kitty cat."

"We rent for the potential to save and buy a house," said Kathe Allen. "It's the American dream, but it's going down the tubes for a lot of people. For us, I hope it's still possible, but it probably is further off for us than in our parents' time."