Joyce Miller of St. Mary's County and Humphrey Ridgely of Charles County have sons who are profoundly retarded. Both parents are now facing an agonizing, sometimes terrifying problem.

Danny Miller is 6; John C. Ridgely is 14. Both are unable to speak, are practically immobilized and helpless without constant care. Someday, their families know, they will no longer be able to provide that care.

It is for this reason, in part, that Humphrey Ridgely has devoted himself for the last six years to a project he helped initiate, the proposed state-operated Southern Maryland Regional Center for the severely and profoundly handicapped.

The proposed $1.3 million facility would be built on a 22-acre campus outside La Plata in Charles County, and would house some 50 retarded persons from Charles, St. Mary's and Calvert counties in seven cottage-like buildings.

But Joyce Miller says Ridgely's project represents "a future without alternatives" for her, because any future for her son in an institution is unacceptable. "When I can't care for him anymore, I want him to be part of the community," she said. "I can't have him put away from everyone else."

Miller has joined with other parents in Charles and Calvert counties in fighting the proposed center, arguing that the money for the facility should be used to create small residential care homes for people like her son.

Because parents like Ridgely and Miller feel so strongly - and so differently - about what services the state should provide for their children, the southern Maryland center, once seen as an essential and ideal facility for the tricounty area, has become the focus of a bitter struggle among mental health advocacy groups and state officials.

It is a contest between two different philosophies about the direction care for the mentally retarded should take.

On the side, Ridgely, members of the Charles County Association for Retarded Citizens and directors of the state's Mental Retardation Administration believe that institutions must be built to care for the most severely handicapped persons in the community.

Institutions, they say, must be only one part of a wide range of services the state provides to the handicapped, but they are necessary for practical and financial reasons.

In contrast, the Calvert and St. Mary's counties associations for Retarded Citizens, and other advocates argue that institutions for the retarded, in any form, are outdated, improper and possibly even unconstitutional.

All services for even the most handicapped persons, they contend, can be provided in small homes and apartments in the community. Each would house only three to six persons and, would be managed by live-in staff.

Both sides are now preparing for what is likely to be the crucial battle: next year, the Assembly will vote on whether to allocate the $1.3 million in construction funds for the center.

Each side feels victory is crucial to the future of mental health facilities in Maryland. "I'm in favor of group homes," says Sen. Jim Simpson of Waldorf, a longtime advocate of the center. "But you have to have both services together, homes and institutions."

"A group home could never provide the proper services for my son," Ridgely says. "It would be far too expensive and its not practical. My son could never be put back into the community, and that's what these homes are for."

"It's not a local issue," says Tom Fisher, director of the Calvert Association for Retarded Citizens. "The community-based programs in Maryland are in the archaic state, and we're about to make it worse."

"They're trying to push my child down the road, away from the community, where they don't have to look at him," says Miller. "He doesn't deserve that - he deserves a home, in the community, like anyone else."

Currently, about 2,700 retarded people are housed in institutions, while slightly more than 300 are involved in community-based programs, ranging from house and apartment arrangements to day-care only programs, according to association for retarded citizens's figures.

State Mental Retardation Administration officials say they are working toward a system of providing care for the mentally retarded that would involve fewer institutions and heavier reliance on community programs.

However, state officials argue that community-based programs are not now capable of coping with the full range of mental retardation problems, and insist that "a continuum" of facilities is needed in the state.

Furthermore, state officials say that the southern Maryland center, which was planned years before community-based programs came into existence, cannot be abandoned because the Maryland legislature and the Charles County community are committed to it.

"There have been major modifications in the plan to reflect the community interest in residential homes," said Dennis Burns, program coordinator for the state Mental Health Administration in the three counties. "We're looking at this as a home environment. The only disparity that exists is that the facility is centrally located.

"If we've got to have an institution," said Roger Harrell, the state coordinator for community service programs for mental retardation, "we're satisfied we've reached a middle point between what the bureaucracy dictates and what the community wants.

"It's not the ideal," Harrell said, "but the legislature is dedicated to this project and we could get more accompolished if we just accepted the fact of the center."

Opponents of the center point out that 75 percent of the state's mental retardation budget, or $42 million, is currently channeled into institutional care, while only $12 million is spent on community service programs.

Currently, only five state-funded group homes existed in Maryland, although six more are planned for the near future, Harrel said.

This budgetary emphasis, opponents say, has been given to institutional care despite the state's plan to move toward residential services, and more importantly, despite recent court decisions indicating that institutional care may now be unconstitutional.

Last year a federal judge in Pennsylvania ruled that mentally retarded persons must be kept in the least restrictice environment available. Under that ruling, the judge announced that persons could not be kept in institutions constitutionally when community service programs were available.

The ruling only to Pennsylvania, and it is being appealed through the court system, but the Association for Retarded Citizens (ARC) leaders believe it sets a precedent for similar court actions in Maryland.

"I don't look at this as an either-or proposition," Burns said. "Residential services are getting started here, and it's just one of the services we can provide."

Burns charged that the controversy over the southern Maryland Center stemmed not from its outmoded conception, but from "parochialism" on the part of the county ARCs.

"They don't like the idea of having one center for three countries," Burns said. "They want a center in their county. If they had gotten acenter in each county, there wouldn't be opposition to this.

"We wouldn't want it even if it was in Calvert," responded Fisher. It would still be an institution and we are opposed to any institutions, anywhere."