All foreign students planning to vacation in the Eastern Hemisphere must leave the United States before December 24 of obtain new visas, Chester H. J. Keppler, Counsellor for Foreign Students, warned yesterday.

Those traveling outside the Americas or Canada have to get different visas.

The New Immigration and Naturalization Law (McCarran Act) passed last June becomes effective on December 24 and has four important changes affecting aliens.

1. Persons with student visas (4-e) or visitors visas (3-2) must obtain new visas if they fail to leave the country before the Act becomes effective. Also, those leaving must still carry the University's form letter which certifies the holder is expected to return for study.

2. Regardless of visas category, all aliens must complete a new Alien Registration form (I-53) during the first ten days of January, 1953 and return it to the nearest Post Office. (These forms will not be available until around January 1.) Penalties for failure to comply include deportation.

3. Except for permanent residents, aliens must continue to submit Address Record Cards (from AR-11) every three months. (Present enforcement of this rule is lax.)

4. Aliens or Exchange Visitors (like Harvard's P-124) may not change their visas to any other type without first returning to their country of origin. Formerly they could go to Canada or Mexico for such a change.

Under the McCarran Act passports must be valied for six months beyond the date for which any U.S. visa is issued. At present passports need only two months' validity.

The Boston Immigration Office last night said as yet it has not received more detailed information about the new visa requirements.