Several hundred students at the University of the District of Columbia, seeking major changes in the way the school is run, stormed into two buildings yesterday and said they would not leave until their demands were met.

The action followed two days of student meetings and signaled a shift in strategy among the protest leaders, who said the board of trustees' failure to meet with them and discuss the university's problems left them no choice but to act.

"I think it's a shame that this would have to occur before the board would take notice of our concerns," said Mark Thompson, one of the protest leaders.

One of the students' key demands is the ouster of 11 trustees, including the board chairman, Nira H. Long. "If you chop off the head of a snake, it dies," Thompson said.

Shortly before noon, the protesters barricaded themselves in the building housing the student center, the radio station and some classrooms, leaving most of the university unaffected by the takeover.

But by midafternoon, what had been a peaceful protest turned confrontational when about 200 students stormed into the adjacent building housing the administrative offices, overcoming a security detail. Night classes subsequently were canceled, and students and university officials appeared to settle in for the night. A university spokesman said a decision would be made overnight as to whether classes would be held today at the Van Ness campus. He said classes would be held at UDC's other two campuses.

The university, which has a student population of about 12,000, has been the focus of angry denunciation since June, when the trustees voted to accept a controversial work of art called "The Dinner Party" and spend more than $1 million to renovate part of the Carnegie Library to house it. The artwork, by feminist artist Judy Chicago, contains some dinner party place settings that a few critics have described as depicting female genitalia.

The board later formed a committee to take another look at the decision, which still threatens $1.6 million in federal funding for the university. Some members of Congress have declared the work obscene.

Students said the "Dinner Party" controversy was only the latest in a string of problems they see in how the university is run. Recently, there has been growing discontent with a failing athletic department, the search to replace Rafael L. Cortada -- the university president fired earlier this year -- and a history of administrative turmoil.

UDC, formed as an open admissions university in 1977, has never had either administrative peace or a broadly accepted set of goals. There have been five presidents or acting presidents in eight years. Several departments have had accreditation problems.

Trustees, administrators and faculty have clashed repeatedly over personnel selections and academic issues. The trustees adopted a 10-year strategic plan for the university that did not include a key proposal supported by Cortada: creation of a two-year community college within the four-year institution.

The students, most of whom come from the District's public schools and many of whom require remedial help to stay in school, had not previously expressed their frustrations with the university's management in so dramatic a fashion.

The protest, which began with a takeover of Building 38 of the Connecticut Avenue NW campus shortly after 11:30 a.m., escalated about three hours later when 200 students forced their way into Building 39, which houses the offices of the administration.

University guards, apparently brought in to prevent a takeover of the second building, were quickly overwhelmed as students rushed past them. The students then went through the administrative offices and asked everyone to leave.

Interim President Miles Mark Fisher IV, who had been in his office throughout the day, encountered some of the students before being escorted out in the afternoon by security guards. He declined to comment on the situation.

"They confronted him on the third floor and asked him to ask the administration to leave and to shut the building down," said university spokesman John H. Britton. "That was the only conversation."

The students submitted 20 demands, including an increase in library hours, better cafeteria services, capital improvements and an Afrocentric curriculum. But, as has been the case in the last several days, the principal demand remained the same: board members must go.

"We could have solved a lot of our problems if we had a permanent president for any length of time," said Gregory Campbell, a freshman. "The board's main purpose is to select a president and let the president do his job. They haven't let a president work and do his job."

After taking over the second building, the students said they would not surrender unless D.C. Mayor Marion Barry immediately requested the resignations of the 11 trustees the mayor's office appoints to the 15-member board. They also asked for the resignation of the student representative to the board, Cynthia Smith, and amnesty for all taking part in the protest.

By 12:20 p.m., about 45 minutes after the students burst in, they were in control of the six levels of Building 38. The students, who had formed an eight-member executive committee, began making telephone calls seeking support.

Among those the students contacted or attempted to contact were Barry; Sharon Pratt Dixon, the Democratic candidate for mayor; and several D.C. Council members.

Last night, Thompson held an impromptu news conference with council members Harry Thomas Sr. (D-Ward 5) and Charlene Drew Jarvis (D-Ward 4) at his side. Neither Thomas nor Jarvis spoke, but Thompson said the protesters had their support.

Thompson also said, without elaborating, that the students expected to meet with the mayor. Earlier, however, a Barry spokeswoman said the matter, for the moment, was between students and the board.

Joseph Webb, the board's alumni trustee, said last night that the board had authorized him to speak to students to help resolve the situation. Webb said he supported the "call for a boycott" of classes, but not necessarily the boycott itself.

Among the students' targets for resignation are Long and Patricia Mathis, two trustees they accuse of being instrumental in the decision to acquire "The Dinner Party."

Efforts to discuss problems with the board have been rebuffed, students said. Monday, the board decided not to call a special meeting and instead said students would be welcome at its regular monthly meeting.

"The board ignored our invitation," said Michael Powell, a sophomore. "They knew the issues we wanted to address in the meeting."

Trustee Concha Johnson said she and fellow members are eager to meet with students: "The students are a very important part of our university, and we want to hear them and listen to their concerns."

Staff writer Ruben Castaneda contributed to this report.