BOSTON (AP) _ The Navy's decision to let two gay ROTC cadets keep their scholarships could signal hope that a Pentagon policy barring homosexuals from the armed services might one day be abolished, activists said Wednesday.

''I think the military realizes that it needs to change and is fully working towards it,'' said discharged cadet Robert Bettiker, a chemistry major at the Massachusetts Institute of Technology.

The Navy had ordered Bettiker and all other ROTC cadets who are homosexuals to reimburse the government for all tuition payments.

But this week, Bettiker and another discharged cadet, Harvard University graduate David Carney, received letters from the Navy exempting them from the tuition demand. The Navy had been seeking $38,612 in tuition from Bettiker and $50,687 from Carney.

''I'm not exactly sure what it all means,'' Bettiker said. ''My lawyer and I will talk and see how this will help other people. I'm willing to do my part.''

Bettiker, 22, had wanted to enter the Navy's Nuclear Propulsion Program, but has instead decided to work at a cancer research laboratory at the University of California, Berkeley after graduation.

Carney, 23, is working toward a masters degree in management at Templeton College in Oxford, England. While in the reserve corps, he was working toward a submarine assignment as a nuclear engineer.

Navy Lt. Greg Smith said ''there was no real information provided'' about the Navy's about-face, but said the decision was related only to the Cambridge students' cases.

The decision ''was handed down on a personal review of the cases that were involved and the Navy elected in these instances to not require them to repay the money,'' Smith said in a telephone interview from Washington, D.C.

Smith said Bettiker and Carney were so far the only two former cadets to receive such a dispensation. He said the decision would not exempt them from the broader Pentagon policy barring homosexuals from ROTC and military service.

Rep. Gerry Studds, D-Mass., who is gay, complained in a letter to Navy Secretary H. Lawrence Garrett III that he had learned of a third homosexual naval ROTC cadet from whom the Navy was seeking repayment.

Studds released his letter but declined to identify the cadet.

''Must I look forward to hearing from midshipman after midshipman who has been ordered to repay funds which - as the Navy acknowledged with regard to Carney and Bettiker - he should not be required to pay?'' Studds wrote.

The Defense Department issued a statement in March saying it views homosexuality as ''incompatible with military service'' for reasons of morale, discipline and security.

Carney said that while he disagrees with the policy, he harbored no animosity about being rejected from the ROTC.

''I don't like the fact that an institution in our American society had this particular policy. But that policy does not make the Navy an institution filled with evil people,'' Carney said in a telephone interview from England.

Mary Bonauto, Bettiker's lawyer, welcomed the Navy's decision but said she was ''looking at it as a crack in a very large wall.''

''They haven't changed their policy, they simply made an exemption,'' she said.

James Holobaugh, a former Army ROTC member at Washington University in St. Louis, was awaiting word on a similar appeal.

Holobaugh, 24, was due to receive his Army commission last May. But after informing his superiors that he had come to the realization that he was gay, an Army professor recommended the cadet be denied commission and be ordered to pay back $25,000 in scholarship money.

''I think it's nice that the Navy admitted that it's wrong for going after the money,'' said Holobaugh, who is enrolled at the University of New Haven in Connecticut. ''But the money is not the issue here.''

Army spokesman Maj. Joseph L. Allred said the Army would consider appeals on a case-by-case basis and would not be swayed by the Navy's recent decisions regarding Bettiker and Carney.