A decade-old, $5 billion federal program intended to transform distressed public housing complexes into healthy, mixed-income neighborhoods fails to adequately support the nation's struggling poor families, according to two studies released yesterday.

Living conditions have improved for a majority of families whose communities were being remade with HOPE VI dollars, said the author of the studies done for the Urban Institute, a Washington-based policy research organization. But some families reported doubling up in order to afford rent in the private market, and many others that remained in public housing or received rent subsidies were struggling to pay rent, buy food and make ends meet.

Researchers found that nearly one-third of families they tried to interview could not be located. They also found that many public housing residents have physical, psychological or other problems that make it difficult for them to take advantage of the self-improvement philosophy underlying HOPE VI efforts to provide job training, repair bad credit and empower residents.

One study said that Congress -- which will decide during the coming year whether to reauthorize HOPE VI for another decade -- should create a new type of transitional housing for the families least able to thrive.

"They're not going to make it in the private housing market, and they're not going to make it in mixed-income housing," lead researcher Susan J. Popkin said yesterday. "We don't have a good alternative right now. We need to think of an alternative."

A public information officer for the U.S. Department of Housing and Urban Development, which administers the program, said the agency was already responding to some issues identified in the report, such as strengthening relocation services.

"The bottom line from this administration is that we think HOPE VI is a positive way to reduce the concentrations of poverty . . . in public housing," Jereon M. Brown said. "We're definitely open to taking a look at the suggested changes."

The studies by the institute provide an in-depth look at how residents are affected by HOPE VI grants, more than 165 of which have been awarded in dozens of communities across the country since 1993.

Five grants, totaling $140 million, have gone to the D.C. Housing Authority. Baltimore has won four, and Alexandria and Hagerstown, Md., each received one.

The findings will be used by lawmakers and advocates as they debate the future of the program, and by individual housing authorities as they implement grants and apply for more.

"HOPE VI . . . does good stuff for neighborhood revitalization. But there is a need for additional housing programs and support services for clients who may have special needs," said Michael P. Kelly, executive director of the D.C. Housing Authority.

The District's East Capitol Dwellings complex was one of five projects included in the second Urban Institute report, a baseline study that will continue through 2005. Residents were interviewed 18 months ago, before relocation began. They will be interviewed again in the spring, and again two years after that.

The other report was based on interviews with 818 households from eight HOPE VI projects across the country -- none from the Washington area. Two had been completely rebuilt and reoccupied, four were partly reoccupied and two were still under construction and vacant.

About one in five of the families interviewed had returned to their rebuilt neighborhoods -- though researchers said that number would probably rise as the remaining projects were completed. One-third were renting in the private market with the help of Section 8 vouchers, and just under one-third were living in other public housing complexes. Nearly one in five had left government-assisted housing.

The study found that those returning to their complexes or remaining in other public housing tended to be older. Younger families, with more children, were more likely to rely on Section 8 vouchers.

Those using vouchers were divided on whether their housing was better than in their old public housing complexes. But large majorities who returned to renovated developments, or moved to other public housing, reported improved conditions.

Several housing advocates who attended the release of the studies yesterday at the Urban Institute's downtown offices said such improvements were to be expected.

"These people were living in what we would all recognize as some of the worst places to live in America," said Wayne Sherwood, co-author of a report earlier this year that sharply criticized the HOPE VI program. "Almost any place they would move would be better. Is that the right standard to use?"

More important, he and others said, were the difficulties encountered in new housing. Nearly two-thirds of families using Section 8 vouchers had a hard time paying rent or utilities, as did half of households living in the private sector without vouchers. And 13 percent of the latter group said they were doubling up with other families to afford a place to live. Many had moved several times since their relocations.

About half of those interviewed said they were struggling to buy food.

"As with welfare reform, the HOPE VI program has the potential to improve former residents' lives," Popkin wrote in an article accompanying the reports. "But it also can put vulnerable families as significant risk."

The complete studies can be found on the institute's Web site, www.urban.org.