ANNAPOLIS, DEC. 5 -- Property assessments in the Maryland suburbs rose sharply over the last three years, state officials said today, even if all recent reports seem to indicate a slump in the local housing market.

State officials said the parts of suburban counties reassessed this year showed dramatic increases from 1987: an average increase of 35.1 percent in Montgomery County, 25.5 percent in Prince George's, 22.5 percent in Howard, 34.8 percent in Charles and 40.8 percent in Anne Arundel. Each piece of property in Maryland is assessed once every three years.

But homeowners should remember that an assessment rise doesn't necessarily mean a higher property tax bill. Although the state sets the assessments, local officials set the tax rates that determine tax bills.

But with 600,000 notices of new assessments to be mailed Monday, officials of the state Department of Assessments and Taxation are braced for another backlash from residents who have watched their traditionally soaring property values flatten out or slip backward in the last few months.

Lloyd Jones, director of the department, said prices aren't going up as rapidly as they were, but some property, notably along waterfronts, is still rising steadily in value. Although property values leveled off in 1989, he said, they increased dramatically in the two years prior to that.

"We've seen the volume of transfers go down about 10 percent, but generally property values are not going down, just leveling off," Jones said.

But those facts seem unlikely to mollify owners in areas such as Montgomery County, where a property tax revolt caught on at this time last year and set in motion a movement to limit tax increases and wide-ranging changes in the county political leadership.

Norman C. Knopf, a Montgomery resident who is treasurer of the organization Fairness in Taxation, predicted a backlash.

"People are going to go through the roof again," Knopf said today. In the past, he said, Montgomery residents consoled themselves about rising taxes with the knowledge that their property values were increasing.

"Now values are going down . . . and then to get on top of that an assessment increase is going to get many peple very angry."

A new feature acting in favor of those paying property taxes, at least homeowners, is the ceiling approved by the 1990 General Assembly. Under that provision, the annual assessment cannot rise more than 10 percent, and counties may set the limit even lower.

Robert Denny, who led the successful fight to limit Montgomery County spending increases to the level of inflation, said the new assessments appear to recognize at least partially the slide in the real estate market.

"The increase is based on the recent past rather than the right now," Denny said. "People had been told a few months ago the average increase in Montgomery was going to be 55 percent, so I'm somewhat relieved."

The increases apply to the one-third of properties in Maryland that were scheduled for reassessment this year under the state's rotating system. Most of the assessments by county were higher last year. The annual increase announced last year in Montgomery, for example, was more than 60 percent over three years for those properties.

In Montgomery, the areas reassessed this year included Rockville, Gaithersburg, Laytonsville, Colesville and part of the Olney election district. In Prince George's, the assessments were clustered inside the Capital Beltway in such communities as Cheverly, Seat Pleasant, Marlow Heights and Landover.