Two incumbents are pitted against each other in one councilmanic district in Prince George's County while there is no incumbent in a second and a third has several challengers, including a former congressman.

As the result of a charter change, the size of the council is being reduced from 11 to 9 members, and all of them will be elected for the first time from districts instead of at large. The matchups for Tuesday's primary election in Districts 1 through 5 were described in yesterday's editions. Here is how the races shape up in the other four districts:

District 6 -- Incumbent Council Chairman Gerard T. McDonough is being challenged in the winding sixth, which includes the largely middle-class, integrated communities of Kettering, Largo, Enterprise Estates and District Heights, by School Board member JoAnn Bell of District Heights.

Bell has raised $6,000, but she is counting on support and name recognition forged through her work on the school board. She criticizes McDonough for his support of the Rosecroft Metro line, and the county's redistricting plan. McDonough has raised nearly $40,000, a third of it from commercial interests.

The district, which is 50 percent black, has been represented by McDonough, a white who is considered one of the council's liberals, as well as a defender of development interests. He repeatedly has called for the modification of TRIM. He emphasizes his record of labor support, his efforts to stop the expansion of a landfill and the contruction of a new jail in his district.

The winner will face an aggressive challenge from unopposed Republican Wilbert Wilson, a black, former Democrat who switched parties after an unsuccessful bid for county council in 1978. Wilson, who already has raised more than $22,000, said at a recent NAACP candidates forum that "zoning and rezoning is the No. 1 problem in this county and Mr. McDonough is leading the charge. His brother is a zoning lawyer."

District 7 -- Originally designed as a safe seat for incumbent council member Deborah Marshall, this 80 percent black, Suitland-centered district is without an incumbent because Marshall decided not to seek reelection. The district, which hugs the D.C. line, includes several of the county's more depressed communities. About 60 percent of its dwellings are apartments, unemployment in some communities runs more than twice the county average and the Seat Pleasant police substation is one of the county's busiest.

Hilda Pemberton, 42, of Landover, was recruited to run by Marshall. She has raised $6,500 from many of the same sources as incumbent members and has been endorsed by nearly all of the area's Democratic officeholders. A deputy director of personnel for the county's hospital administration, she supports modification of TRIM and stresses her ability to work with the council to defend district interests.

Robert A. Spencer, 49, owner of a photography and audio-visual company, has picked up the endorsements of elected officials in the Seat Pleasant and Capitol Heights as well as three county newspapers. Spencer said he decided to run "because machine politicians weren't looking out for the district the way they should." Spencer said he would press the county to establish a repeat offenders court and a department of labor to provide job training. Spencer said he only supports the modification of TRIM as a last resort.

Charles E. Francis, 29, a deputy sheriff from Capitol Heights, has attacked both of his foes for their endorsements, Pemberton for appearing on the literature of several "organization" state senators, and Spencer for his endorsement by councilwoman Sue Mills. Francis, who has raised less than $200, wants to hire more police, fire fighters, sheriffs and other public safety workers. But, he said, he does not support the Plus 4 amendment to TRIM because of its cost.

The Democratic nominee will face unopposed Republican Melvinor Williamson-Gray, a research analyst with the county police.

District 8 -- The triangular district, including Marlow Heights, Camp Springs, Oxon Hill and Temple Hills, pits two incumbents because of a redistricting plan designed to remove Sue V. Mills from her antibusing, Oxon Hill home base. But Mills, using property in another part of the district, has survived that scheme and is giving fellow incumbent David Hartlove a run. Hartlove has the backing of the county's incumbent Democratic senators, the Chamber of Commerce and development interests, although Mills also has received contributions from developers and zoning lawyers.

A third, perennial candidate, retired police officer John Eugene Sellner, plans to spend less than $100 compared with more than $40,000 by both Mills and Hartlove. Sellner would establish an auxiliary corps of retired police officers..

The Democratic winner will have two opponents in the general election, independent Joseph Johnson, and Republican Louis Cross.

District 9--Development will be an issue for years in this district, which covers the rural southern third of the county plus the affluent suburbs of Tantallon, Fort Washington and Fort Foote and Andrews Air Force Base.

Incumbent William B. Amonett, a real estate broker from Brandywine, is being challenged by Carmen E. Anderson and William D. Burlison. Amonett is backed by development interests and has support of incumbent state senators, particularly Thomas V. (Mike) Miller.

Anderson is a registered nurse and well known antidevelopment citizen activist who opposes any modification of "TRIM" because she says the county does not now properly spend the funds it has. She has raised only $5,178 compared with Amonett's $34,020. Burlison, a former six-term congressman from Missouri, has raised $13,867, most from Missouri.

The Democratic winner is likely to face a strong challenge from unopposed Republican Ella Enis, a former aide to county executive Lawrence J. Hogan.