The robust housing market that is boosting home prices nationwide is also adding to property values in Southern Maryland, according to government officials and real estate agents.

However, increases in home values have lagged behind the Maryland average in two of the region's three counties, according to state real estate assessors. The assessors estimate values that are used to set property taxes.

In 1999, they found that compared with three years earlier, values had risen an average of 3.6 percent among houses they examined in Charles County.

In St. Mary's County, the values had risen an average of 4.3 percent during the past three years, while in Calvert County they had risen an average of 6 percent, according to calculations by the state Department of Assessments and Taxation.

The figures represent a continuation of property appreciation in the region. A year ago, state assessors found that during the three-year period, values had increased 2.5 percent in Charles County, 6.5 percent in St. Mary's County and 3.6 percent in Calvert County.

The year-to-year figures are not strictly comparable because state assessors check values in a different third of each county each year. It thus takes them three years to work back around to the same houses.

For instance, in Charles County assessors this year will be examining homes in the Waldorf area. The assessors last examined that area in 1997 and issued a report finding that values had dropped 2 percent since 1994.

That report helped make housing values a leading issue in recent county politics and lent impetus to elected commissioners' decisions to craft regulations restricting town house development and to tie housing growth tightly to public school capacity.

In their work during 1999, state assessors found that in all of Maryland, values had risen an average of 5.7 percent over three years.

Two-thirds of Maryland's homes experienced an increase in value, with the remaining third flat or declining in value, the Department of Assessments and Taxation said.

Citing what it called "the hot real estate market of recent years," the department said record numbers of home buyers had bid up prices for a dwindling housing stock on the market.

For homeowners, the department's figures mean that assessments used by tax authorities likely will rise annually for three years by roughly one-third of the increase in value. County governments can anticipate a corresponding increase in revenues.

Real estate agents and state assessors said that in Southern Maryland, the rise in value was tied to demand generated mainly by two sources: the traditional commuter-driven market, and the recently expanded job base surrounding the Patuxent River Naval Air Station in St. Mary's County.

"The market's been brisk for the past year," said Fred Darney, a real estate agent with O'Conor Piper and Flynn's office in Lexington Park, in St. Mary's County. "There are certain little pockets that have stagnated, but there are other pockets that have gone up 10 percent."

Darney said some workers, drawn to the thousands of jobs added at the Navy base during the 1990s, had tired of renting and had begun looking to buy homes.

In St. Mary's County, assessors inspected homes in the southern third of the county, including the Lexington Park area, said James W. Spense, supervisor of assessments for the county.

Much of the real estate activity there involved new homes, which seem to be preferred by many newcomers drawn to jobs related to the Navy base, Spense said.

But part of that demand spilled over into existing homes, helping to raise their values, too, Spense said.

"There's been a gradual increase in the overall value," he said.

In Charles County, assessors worked in the eastern part of the county last year, including Hughesville, the La Plata area and areas to the south.

Don Cox, vice president for Baldus Real Estate in La Plata, said he was surprised state assessments did not reflect stronger increases in value.

"In the last year, the average price of a house we sold countywide was up 11 percent," Cox said.

Cox said many professional couples are buying homes for $300,000 or more in the Hughesville-Bryantown area. Often one family member will travel to a Navy-related job near Lexington Park and the other will head to the Washington metro region for work, he said. "They're splitting the difference, distance-wise," Cox said.

As in St. Mary's County, the effects of strong demand were not limited to new homes. Cox said he knew of homeowners who received notice that their home's value had risen by 10 percent.

In Calvert County, assessors covered Solomons, Lusby, Broomes Island and other areas in the southern third of the county last year.

In those areas, too, robust demand led to increased values, said Susan J. Kopanke, the county's supervisor of assessments.

"Calvert County continues to be a growth area," Kopanke said. "It's a healthy, active market."