American University, pressed by student demands for more housing, has purchased the Glover Tunlaw Apartments for $1,260,000 and plans to turn the 63-unit building into a dormitory.

Present tenants of the building, nearly a mile from the AU campus at 2725 39th St. NW, have been told to vacate their apartments within 90 days. University officials said those with leases running past that deadline could remain longer. They also promised to help elderly tenants and others facing hardships to find new housing.

But at least some of the tenants plan to fight eviction. They are retaining the Kass, Skalet and Frosh law firm to represent them.

The purchase, consummated last Thursday, marks the university's first acquisition of off-campus property for student housing. In 1973, Georgetown University paid $5.4 million for the Alban Towers apartment-hotel, and last March George Washington University bought the Francis Scott Key Hotel - both moves to house more students.

Officials at all three campuses said yesterday that more students want to live in dormitories than the universities can accommodate. Gerogetown has some 600 undergratues on its dormitory waiting lists, a spokesman said.

Here and nationally, students have been flocking back to campus dorm rooms in the past few years after finding off-campus rental housing scarce and costly. Moreover, many universities have relaxed once-strict rules on visiting hours by members of the opposite sex and other facets of dormitory life - making campus housing more attractive.

This reverses a trend of the late 1960s, in the heady campus protest days, when restless undergraduates deserted dorms in droves for the freedoms of off-campus living while universities with vacant rooms fretted about lost revenues.

To minimize tenant unrest at the Glover Tunlaw partments, AU's R. Bruce poynter, university chaplain and assistant to the provost, is offering help particularly to older, frailer occupants who may have trouble relocating.

"The university is not going to be disposed to be hardnoosed about evicting people on the 90th day," Poynte said. But AU does plan to start housing students in the building this fall.

A spokeswoman also stressed that AU authorities plan to leave the building on the city's property-tax rolls, though the university as a tax-exempt institution could seek to withdraw it.

The 63-one-bedroom and tow-bedroom apartments could accommodate more than 200 students, depending on city occupancy restrictions, the spokeswoman said. Students will be charged at rates comparable to those for campus dormitory rooms, she added.