A national fraternity is conducting a major recruiting drive to add to its three-year-old Harvard chapter, which now has only four members, organizers said yesterday.

About 20 male Harvard students, mostly freshmen, have pledged to join the local branch of Zeta Psi, which is not recognized by the University. The national organization has 52 chapters in North America including branches at most Ivy League schools, said Daniel J. Ramos '91, the local chapter's vice president.

The fraternity does not have a physical base in Cambridge. Members said the group holds weekly meetings in members' rooms and they plan to throw parties and may sponsor a sports tournament.

Under University rules, fraternities cannot be recognized as official student organizations, said Dean of Students Archie C. Epps. "We have a policy against single sex institutions," Epps said, adding that Harvard groups also cannot be affiliated with national organizations. Only recognized student groups can use Harvard's name and facilities, Epps said.

The fraternity will not seek official recognition from the University but it is recognized by Zeta Psi's national headquarters, said Steven M. Cohn '91, recently elected president of the Harvard chapter. Under national rules, the group must be all male. The Brown University chapter is no longer affiliated with the national organization because it now admits women.

The fraternity's revival comes at a time when Harvard's traditional all-male social organizations, the final clubs, have come under attack. Lisa J.Schkolnick '88 this December filed adiscrimination complaint against one of the nineclubs. The senior claims she has been denied animportant part of the Harvard experience by notbeing allowed to join one of the clubs.

But Zeta Psi members said that the fraternitydiffered from the final clubs. Zeta Psi is "not afinal club with a different name," Ramos said,because "we are not an exclusive group." He saidthe group's activities would be open to people whowere not members of the fraternity.

"The basis of selection was guys we thoughtwould be committed," Cohn said. He added that thefraternity's national affiliation furtherdifferentiates it from the final clubs. Althoughthe national headquaters does not give money tothe chapters, Walton said it does advise thechapter members and gives out scholarships.

A Zeta Psi chapter existed at Harvard duringthe late 19th century but died off in the 1880s.When the national organization beganreestablishing its Harvard chapter three yearsago, it asked the University for help, said M.Lauck Walton, director of administration at thefraternity's New York headquarters.

"There was an uproar," Walton said. "It'spurposeless for us to go ask [for help fromHarvard]." He added that the chapter's unofficialstatus would not be a problem. Zeta Psi'sPrinceton chapter is also not affiliated with itsschool, he said.

The Harvard group got going in 1985, and thechapter flourished for a while. However, most ofits members graduated last spring. In an attemptto revitalize the chapter, the nationalorganization sponsored a reception at the CharlesHotel this fall, Ramos said.

New members of Zeta Psi said they joined thegroup in order to have a close group of friends.Calling the group a "single unit," Cohn said,"With the fraternity, we stress brotherhood."

"From my experience [as an undergraduate memberof a fraternity], I learned a lot," Walton said,adding "a lot of people find that."

Zeta Psi will work with chapters at Tufts andMIT in planning fundraisers and other activities,Cohn said. He said the group would also holdsocial events, either small parties in members'rooms or at off-campus locations.

Cohn said he "knew a lot of people againstfraternities," but added, that there are also "alot for them." He said a national sorority, KappaAlpha Theta was interested in coming to Harvard.

The local Zeta Psi chapter may need approvalfrom Cambridge authorities in order to carry outsome of its plans, members said. According toCohn, an alumni group representing the chapterwould speak with Cambridge authorities "soon.