When you leave the U.S., you will surrender your I-94 to the immigration inspector. The next time you return, you’ll be issued a new I-94, and you will use the same admission number as previously issued.
In order to re-enter the U.S., you must have a valid passport; a current, validated DS-2019; and a valid J-1 visa.
The validating signature at the bottom of the first page of your DS-2019 is officially valid for one year, but it is STRONGLY recommended that you have it validated each semester. J-1 visitors needing a new signature/form for travel should bring their DS-2019 to the International Office at least one week PRIOR to departure.
Exception: Students traveling to Canada, Mexico, or adjacent islands (excluding Cuba) are not expected to surrender their I-94 cards if they plan to re-enter the U.S. within the 30-day time frame. Students may re-enter the country after a trip of 30 days or fewer, provided they have the above- mentioned documents and their I-94.
Once within the borders of the U.S., if your J-1 visa has expired, and you plan to go to Canada, Mexico or one of the Caribbean islands (other than Cuba), it will not be necessary to apply for a new visa to re-enter the U.S. It is always advisable that exchange visitors talk to the International Student Advisor before traveling outside the U.S.