The contrasts between the old and the new in the northwestern Prince George's County neighborhood of Langley Park are most obvious in the Langley Park-McCormick Elementary School and the Langley Park Senior Citizens Center.

At the school, which draws its students from within a mile of the building on 15th Avenue, Principal Lee Meiners presides over a diverse student body whose members speak 17 languages and represent 33 countries.

Most of the foreign-born pupils -- who make up half the total 611 students -- are from Central and South American nations, with many of the others coming from Jamaica, India, Cambodia, Haiti and Nigeria.

Forty yards from the school is a center for senior citizens. A majority of the dozens of older people who frequent the low-rise building are longtime Langley Park residents.

Separated by barriers of language and customs, the senior citizens and the newcomers had little to do with each other for a long time.

Within the past year, however, the groups have had more contact because some of the senior citizens are tutoring the elementary school students in English.

Nancy Allison, a teacher at the elementary school for 17 years, has watched the changes during the 25 years she and her husband Maurice have lived in Langley Park.

"The biggest change is in the people," Nancy Allison said. "We are an international community now."

The internationalization started in the 1970s in Langley Park, an area bordered by New Hampshire Avenue, University Boulevard, Riggs Road and the Northwest Branch Creek.

As recently as 1970, Spanish was the first language for 6.1 percent of the Langley Park population, according to a 1974 county government publication.

In 1980, the U.S. Census Bureau reported, 13.4 percent of the residents spoke Spanish as a first language.

The newcomers fill most of the garden apartments around 15th Avenue, 14th Avenue and Merrimac Drive, paying rents ranging from about $475 for a one-bedroom unit to $675 for a three-bedroom apartment.

The three-bedroom bungalows and two-story garden apartments that make up much of the other housing in the neighborhood were built in the 1940s for returning World War II veterans.

Many of the single-family houses are passed from generation to generation. Langley-Hampshire Civic Association President Matt Dorman, for example, lives in the house his grandparents bought.

There is very little room for new development in the area, and houses bring an average price of $94,000, according to Sterling Mehring, manager of the Takoma Park office of Long & Foster Realtors.

The diversity in the neighborhood is one factor that has kept the Allison family in Langley Park, Nancy Allison said, even though many of her neighbors have moved out over the years.

But sales of illegal drugs have increased in the area, spurring some longtime residents to move away, Allison and other Langley Park residents said. Drug sales are heaviest in and around apartment complexes at the 14th Avenue and Kanawha Street area.

Police call the area an "open drug market" that generates other crimes, including shootings and muggings.

But some criminal activity has declined this year, a police spokesman said. Reported burglaries dropped from 61 during the first half of last year to 35 during the same period in 1987, and reported robberies declined from 29 to 23 during the same period.

Other types of crime continue at about the same rate. Thefts from cars are among the most frequent crimes, with 40 reported during the first six months of last year compared with 33 in the same period this year. A police "action team" of four to six officers is working with members of the community to combat the drug sales and other crimes.

Allison said the drug problems are "upsetting because this has been such a nice, quiet neighborhood. We've considered moving many times, but each time we've decided we like it where we are."

The area is about two miles south of the Capital Beltway's New Hampshire Avenue interchange and only minutes away from the Takoma Park Metro station.

New Hampshire and University Boulevard are major arteries in Prince George's County, and frequent Metro bus service is available on both roads.

Large shopping centers occupy four corners of the intersection of University Boulevard and New Hampshire Avenue, and the stores include a 24-hour, remodeled Safeway complete with a fresh seafood counter, deli, bakery and a large bulk food section.

A 24-hour Giant and an all-night Peoples Drug Store are nearby. In all, the centers provide shoppers with more than 60 stores that offer shoes, furniture, entertainment, clothing jewelry and flowers.

On the northern edge of Langley Park is one of the area's little-known treasures: the Northwest Branch Stream Valley Park, which features a five-mile trail for joggers, bicyclists, hikers and equestrians along the Northwest Branch Creek.

The trail passes the historic Adelphi Mill and Storehouse, a two-story stone mill built in 1796 that is the oldest and largest mill of its type in the Washington area, according to the county government.

The winding trail starts in Montgomery County, about one mile west of New Hampshire Avenue, passes south of the Holy Trinity Mission Seminary and near the University of Maryland and ends at the Ager Road Neighborhood Park in Hyattsville.

Plans are on the board for the trail to continue past the planned West Hyattsville Metro stop to Magruder Park in Hyattsville and to connect with the Northeast Branch Creek through Riverdale and College Park, according to a Prince George's planning commission official.

"I think it is an ideal location to live," said Dorman. "A lot of people point out that there are a lot of problems in Langley Park, especially with crime. I don't think it is a problem that can't be overcome."

Representatives of dozens of private and public organizations have started meeting monthly to discuss ways to deal with the crime problems and the extra burden it places on the many apartment dwellers who do not speak English.

The neighborhood, which also has its own Boys Club and Girls Club, sponsors an annual Hispanic festival and a community festival. Both events are designed to draw Langley Park's newer and older residents together to talk about problems.

"People are working to make things better," Allison said. "For the most part, things are looking up."