The College Park campus of the University of Maryland, prompted by long-standing concerns about alcohol abuse as well as by recent incidents, has told its fraternities and sororities that they can no longer sponsor beer parties during the week.

The new regulations, which were adopted Friday and took effect immediately, go beyond a controversial alcohol policy enunciated only last spring that barred beer kegs and punch bowls from all fraternity and sorority functions.

The new rules still permit weekend beer parties, although with restrictions.

"We want to address the abuse of alcohol in our environment," said William L. "Bud" Thomas Jr., vice president for student affairs at the College Park campus, which enrolls more than 25,000 students.

In restricting the serving of alcohol to weekend social functions and in extending the university's conduct code to private and off-campus organizations, the regulations appear to be among the most stringent at major American colleges and universities.

They come at a time of rising national concern about alcohol abuse, and amid efforts to sharply improve the academic standing of the College Park campus.

Thomas said yesterday that during the first few weeks of the fall semester, a long-term understanding on the alcohol issue between the administration and the Greek groups "seemed to be ignored."

While the ban on kegs and punch bowls apparently was respected, he said, parties were held that were open to all, rather than only members and guests.

In addition, fraternity and sorority leaders working to hammer out new alcohol policies were harassed, and several large and poorly managed parties were held, Thomas said.

Thomas said that he proposed new regulations, and that the Interfraternity Council and the Panhellenic Association -- the umbrella groups for the Greek-letter organizations -- answered by proposing their own measures.

The student proposal, which he said was more far-reaching than the university's own, was adopted Friday, Thomas said.

One feature of the fraternity and sorority proposal permits beer parties to be held on Thursdays by those groups that have grade-point averages above those of the campus-wide men's or women's average for the previous year.

In addition, in recognition of Homecoming Week, which begins today, alcohol may be served during restricted hours at social events held on Wednesday and Thursday, regardless of grade-point averages.

According to Thomas, a rule issued in June that barred kegs and punch bowls from any Greek-sponsored parties this semester was prompted by university officials' belief that the serving of alcohol from such containers fosters increased consumption.

Fraternities and sororities accepted those new regulations publicly, but some members grumbled in private.

In the past, Thomas said, Greek organizations "were expected to exercise a great deal" of self-discipline. The new regulations move beyond this position to make the organizations' behavior part of the university's code of conduct.

In addition to restricting the nights on which the groups may formally sponsor gatherings at which alcohol is served, Thomas said the new rules restrict attendance at the gatherings, ending so-called "open" parties.

He said infractions could trigger a campus judicial process that could lead to a range of sanctions.