John G. Milliken, officially elected yesterday as chairman of the all-Democratic Arlington County Board for 1988, announced he would make parks and recreation a top priority in the coming year.

Other members of the five-member board, which held its traditional New Year's Day organizational meeting, named affordable housing, controlled development, transportation, schools and drug abuse treatment as areas needing attention.

The chairman is elected annually by the board. Though the added duties of the chairman are largely ceremonial, he or she has more visibility. As a result, the role generally is given to a member of the majority who is up for election.

Milliken, whose board term expires this year, has said he is considering running against Rep. Frank R. Wolf (R-Va.) again this year. He lost a race against Wolf in 1986.

Milliken's focus on parks in part reflects the stable, largely residential character of Arlington County, home to some 155,000 people.

"Arlington is a mature community. Our land-use decisions are made. The political battles that rock other jursidictions are behind us," Milliken said in a prepared statement.

With reliable services and low taxes, "our concentration over the past several years has been on the livability of the community, those extra things that make and keep Arlington a nice place to live, work and raise a family," he said.

Declaring 1988 "the year of celebrating Arlington outdoors," the new chairman said he plans to stock Four Mile Run, a stream that flows through the county, with trout for fishing. He also said that a new Gateway Park would be dedicated at Key Bridge in the fall and that new sections of bike paths would be opened.

As Milliken spoke, about a dozen people in the audience held signs calling for more money for affordable housing in Arlington, an issue that dominated much of the county's attention in 1987. Last year, the board raised the percentage of county revenues devoted to housing from 1 percent to 2 percent, and Milliken said after the meeting that that level most likely would be maintained this year.

Outgoing board chairman Albert C. Eisenberg, reelected in the fall to a four-year term, had made housing his top priority and said yesterday this remains a key issue.

"Too many people find it costs too much to live here . . . . It's sure to get worse," Eisenberg said. "We ought to maintain and if possible increase the amount dedicated to housing." He said the state and developers should make more contributions to that effort.

William T. Newman, the one new member and the first black to serve on the board since Reconstruction, said at his first meeting that he would like to see Arlington's government made more accessible to the entire community, and proposed creation of a county human rights commission. Newman called for more attention on punishing drug dealers and providing drug treatment facilities for addicts.

With Newman's election and the retirement of Republican Michael E. Brunner, the board is composed entirely of Democrats for the first time in more than a decade. Hoping to diffuse concerns that Republicans would be cut out of the process, Milliken said the chairman of the Arlington County Republican Party will nominate people to fill certain vacancies on boards and commissions.