If you have applied for a STEM OPT extension, but you have not yet received the new OPT card, you may be able to re-enter the U.S. if your current period of OPT is unexpired when you re-enter, and you have proof of the filing of the STEM OPT application (the receipt notice from the government, and a copy of the application packet). In addition, you should have proof of temporary employment with an E-Verify employer. Note that you would also need a valid F-1 student visa to re-enter the U.S. If you have applied for the STEM OPT card, and have not received it, and your current period of OPT has expired, it may be very risky to travel and re-enter the U.S., as you will not have the new OPT work card in your possession. If you must travel, be sure to have your proof of the filing of the STEM OPT application (the receipt notice from the government, and a copy of the application packet). In addition, you should have proof of temporary employment with an E-Verify employ...