College spokesman James Leach said the purchases were recommended by a task force formed after a drunk-driving accident left four people dead and the driver in prison for vehicular manslaughter.

"There have been sexual assaults, hazing, violent fights and a pattern of problems over the years. Many people thought change was necessary,'' Leach said. "The task force looked at several options, including eliminating the Greek system. Instead, it recommended a way for the university to assert greater control, and still give students authority over their operations.''

Under the plan, almost all students would have to live in university-owned housing. Any Greek organization that retained ownership of its property would lose university recognition.

Opponents call the plan an attempt to end the Greek system on campus and students and alumni planned to rally against it Tuesday. About 40 percent of Colgate's students belong to a fraternity or sorority.

"They are acting like corporate bullies instead of a university,'' said senior Sean Devlin, of Connecticut, a member of Delta Kappa Epsilon.

Charles Sanford, a trustee emeritus who graduated from Colgate in 1958, has formed Student & Alumni for Colgate to oppose the college's plan. "They are being coerced into giving up their property rights - or face extinction,'' Sanford said.

Most of the university's Greek houses have agreed to sell. Two of the three fraternities that refused are currently inactive.

The third, DKE, filed a federal lawsuit in February accusing the university of violating antitrust and monopoly laws and students' rights, said attorney Tom Weincek, a former DKE president and Colgate graduate.

In 2001, Colgate shut down DKE for a year for serving alcohol to the driver in the crash that killed four people.